diff --git a/autotests/libs/CMakeLists.txt b/autotests/libs/CMakeLists.txt
--- a/autotests/libs/CMakeLists.txt
+++ b/autotests/libs/CMakeLists.txt
@@ -159,7 +159,6 @@
 add_akonadi_isolated_test(SOURCE cachetest.cpp)
 add_akonadi_isolated_test(SOURCE collectionjobtest.cpp)
 add_akonadi_isolated_test(SOURCE collectionmodifytest.cpp)
-add_akonadi_isolated_test(SOURCE referencetest.cpp)
 
 # FIXME: This is very unstable on Jenkins
 #add_akonadi_isolated_test(servermanagertest.cpp)
diff --git a/autotests/libs/collectionjobtest.h b/autotests/libs/collectionjobtest.h
--- a/autotests/libs/collectionjobtest.h
+++ b/autotests/libs/collectionjobtest.h
@@ -54,7 +54,6 @@
     void testAncestorRetrieval();
     void testAncestorAttributeRetrieval();
     void testListPreference();
-    void testReference();
 };
 
 #endif
diff --git a/autotests/libs/collectionjobtest.cpp b/autotests/libs/collectionjobtest.cpp
--- a/autotests/libs/collectionjobtest.cpp
+++ b/autotests/libs/collectionjobtest.cpp
@@ -903,54 +903,4 @@
     AKVERIFYEXEC(deleteJob);
 }
 
-void CollectionJobTest::testReference()
-{
-    Akonadi::Collection baseCol;
-    {
-        baseCol.setParentCollection(Akonadi::Collection(res1ColId));
-        baseCol.setName(QStringLiteral("base"));
-        Akonadi::CollectionCreateJob *create = new Akonadi::CollectionCreateJob(baseCol);
-        AKVERIFYEXEC(create);
-        baseCol = create->collection();
-    }
-
-    {
-        Akonadi::Collection col;
-        col.setParentCollection(baseCol);
-        col.setName(QStringLiteral("referenced"));
-        col.setEnabled(false);
-        {
-            Akonadi::CollectionCreateJob *create = new Akonadi::CollectionCreateJob(col);
-            AKVERIFYEXEC(create);
-            CollectionFetchJob *job = new CollectionFetchJob(create->collection(), CollectionFetchJob::Base);
-            AKVERIFYEXEC(job);
-            col = job->collections().first();
-        }
-        {
-            col.setReferenced(true);
-            Akonadi::CollectionModifyJob *modify = new Akonadi::CollectionModifyJob(col);
-            AKVERIFYEXEC(modify);
-            CollectionFetchJob *job = new CollectionFetchJob(col, CollectionFetchJob::Base);
-            AKVERIFYEXEC(job);
-            Akonadi::Collection result = job->collections().first();
-            QCOMPARE(result.enabled(), false);
-            QCOMPARE(result.referenced(), true);
-        }
-        {
-            col.setReferenced(false);
-            Akonadi::CollectionModifyJob *modify = new Akonadi::CollectionModifyJob(col);
-            AKVERIFYEXEC(modify);
-            CollectionFetchJob *job = new CollectionFetchJob(col, CollectionFetchJob::Base);
-            AKVERIFYEXEC(job);
-            Akonadi::Collection result = job->collections().first();
-            QCOMPARE(result.enabled(), false);
-            QCOMPARE(result.referenced(), false);
-        }
-    }
-
-    //Cleanup
-    CollectionDeleteJob *deleteJob = new CollectionDeleteJob(baseCol);
-    AKVERIFYEXEC(deleteJob);
-}
-
 #include "collectionjobtest.moc"
diff --git a/autotests/libs/etmpopulationtest.cpp b/autotests/libs/etmpopulationtest.cpp
--- a/autotests/libs/etmpopulationtest.cpp
+++ b/autotests/libs/etmpopulationtest.cpp
@@ -139,9 +139,7 @@
     void testAddMonitoringCollections();
     void testRemoveMonitoringCollections();
     void testDisplayFilter();
-    void testReferenceCollection();
     void testLoadingOfHiddenCollection();
-    void testSwitchFromReferenceToEnabled();
 
 private:
     Collection res;
@@ -319,50 +317,6 @@
     AKVERIFYEXEC(deleteJob);
 }
 
-void EtmPopulationTest::testReferenceCollection()
-{
-    Collection col5 = createCollection(QStringLiteral("col5"), monitorCol, false);
-    QVERIFY(col5.isValid());
-
-    ChangeRecorder *changeRecorder = new ChangeRecorder(this);
-    InspectableETM *model = new InspectableETM(changeRecorder, this);
-    model->setItemPopulationStrategy(EntityTreeModel::ImmediatePopulation);
-    model->setCollectionFetchStrategy(EntityTreeModel::FetchCollectionsRecursive);
-    model->setListFilter(Akonadi::CollectionFetchScope::Display);
-
-    QTRY_VERIFY(model->isFullyPopulated());
-    QVERIFY(!getIndex(QStringLiteral("col5"), model).isValid());
-    //Check that this random other collection is actually available
-    QVERIFY(getIndex(QStringLiteral("col1"), model).isValid());
-
-    ModelSignalSpy spy(*model);
-
-    //Reference the collection and it should appear in the model
-    model->setCollectionReferenced(col5, true);
-
-    QTRY_VERIFY(getIndex(QStringLiteral("col5"), model).isValid());
-    QTRY_VERIFY(getIndex(QStringLiteral("col5"), model).data(Akonadi::EntityTreeModel::IsPopulatedRole).toBool());
-    //Check that this random other collection is still available
-    QVERIFY(getIndex(QStringLiteral("col1"), model).isValid());
-    //Verify the etms collection has been updated accordingly
-    QTRY_VERIFY(getIndex(QStringLiteral("col5"), model).data(Akonadi::EntityTreeModel::CollectionRole).value<Akonadi::Collection>().referenced());
-
-    //Ensure all signals have been delivered to the spy
-    QTest::qWait(0);
-    QCOMPARE(spy.mSignals.count(QStringLiteral("rowsInserted")), 1);
-    //Signals for data-changed signal from the referencing
-    QCOMPARE(spy.mSignals.count(QStringLiteral("dataChanged")), 2);
-
-    //Dereference the collection and it should disappear again
-    model->setCollectionReferenced(col5, false);
-    QTRY_VERIFY(!getIndex(QStringLiteral("col5"), model).isValid());
-    //Check that this random other collection is still available
-    QVERIFY(getIndex(QStringLiteral("col1"), model).isValid());
-
-    Akonadi::CollectionDeleteJob *deleteJob = new Akonadi::CollectionDeleteJob(col5);
-    AKVERIFYEXEC(deleteJob);
-}
-
 /*
  * Col5 and it's ancestors should be included although the ancestors don't match the mimetype filter.
  */
@@ -384,34 +338,6 @@
     AKVERIFYEXEC(deleteJob);
 }
 
-void EtmPopulationTest::testSwitchFromReferenceToEnabled()
-{
-    Collection col5 = createCollection(QStringLiteral("col5"), monitorCol, false, QStringList() << QStringLiteral("application/test") << Collection::mimeType());
-    QVERIFY(col5.isValid());
-    Collection col6 = createCollection(QStringLiteral("col6"), col5, true, QStringList() << QStringLiteral("application/test"));
-    QVERIFY(col6.isValid());
-
-    ChangeRecorder *changeRecorder = new ChangeRecorder(this);
-    InspectableETM *model = new InspectableETM(changeRecorder, this);
-    model->setItemPopulationStrategy(EntityTreeModel::ImmediatePopulation);
-    model->setCollectionFetchStrategy(EntityTreeModel::FetchCollectionsRecursive);
-    model->setListFilter(Akonadi::CollectionFetchScope::Display);
-    QTRY_VERIFY(model->isFullyPopulated());
-    model->setCollectionReferenced(col5, true);
-    QTRY_VERIFY(getIndex(QStringLiteral("col5"), model).data(Akonadi::EntityTreeModel::CollectionRole).value<Akonadi::Collection>().referenced());
-
-    //Dereference and enable the collection
-    col5.setEnabled(true);
-    model->setCollectionReferenced(col5, false);
-
-    //Index and child should stay in model since both are enabled
-    QVERIFY(getIndex(QStringLiteral("col5"), model).isValid());
-    QVERIFY(getIndex(QStringLiteral("col6"), model).isValid());
-
-    Akonadi::CollectionDeleteJob *deleteJob = new Akonadi::CollectionDeleteJob(col5);
-    AKVERIFYEXEC(deleteJob);
-}
-
 #include "etmpopulationtest.moc"
 
 QTEST_AKONADIMAIN(EtmPopulationTest)
diff --git a/autotests/libs/referencetest.h b/autotests/libs/referencetest.h
deleted file mode 100644
--- a/autotests/libs/referencetest.h
+++ /dev/null
@@ -1,34 +0,0 @@
-/*
-    Copyright (c) 2006 Volker Krause <vkrause@kde.org>
-
-    This library is free software; you can redistribute it and/or modify it
-    under the terms of the GNU Library General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or (at your
-    option) any later version.
-
-    This library is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
-    License for more details.
-
-    You should have received a copy of the GNU Library General Public License
-    along with this library; see the file COPYING.LIB.  If not, write to the
-    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-    02110-1301, USA.
-*/
-
-#ifndef REFERENCETEST_H
-#define REFERENCETEST_H
-
-#include <QObject>
-
-class ReferenceTest : public QObject
-{
-    Q_OBJECT
-private Q_SLOTS:
-    void initTestCase();
-    void testReference();
-    void testReferenceFromMultiSession();
-};
-
-#endif
diff --git a/autotests/libs/referencetest.cpp b/autotests/libs/referencetest.cpp
deleted file mode 100644
--- a/autotests/libs/referencetest.cpp
+++ /dev/null
@@ -1,238 +0,0 @@
-/*
-    Copyright (c) 2006 Volker Krause <vkrause@kde.org>
-
-    This library is free software; you can redistribute it and/or modify it
-    under the terms of the GNU Library General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or (at your
-    option) any later version.
-
-    This library is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
-    License for more details.
-
-    You should have received a copy of the GNU Library General Public License
-    along with this library; see the file COPYING.LIB.  If not, write to the
-    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-    02110-1301, USA.
-*/
-
-#include "referencetest.h"
-
-#include <sys/types.h>
-
-#include <qtest_akonadi.h>
-#include "test_utils.h"
-
-#include "agentmanager.h"
-#include "agentinstance.h"
-#include "cachepolicy.h"
-#include "collection.h"
-#include "collectioncreatejob.h"
-#include "collectiondeletejob.h"
-#include "collectionfetchjob.h"
-#include "collectionmodifyjob.h"
-#include "control.h"
-#include "item.h"
-#include "collectionfetchscope.h"
-#include "session.h"
-#include "monitor.h"
-
-using namespace Akonadi;
-
-QTEST_AKONADIMAIN(ReferenceTest)
-
-void ReferenceTest::initTestCase()
-{
-    qRegisterMetaType<Akonadi::Collection::List>();
-    AkonadiTest::checkTestIsIsolated();
-    Control::start();
-    AkonadiTest::setAllResourcesOffline();
-}
-
-static Collection::Id res1ColId = 6; // -1;
-
-void ReferenceTest::testReference()
-{
-    Akonadi::Collection baseCol;
-    {
-        baseCol.setParentCollection(Akonadi::Collection(res1ColId));
-        baseCol.setName(QStringLiteral("base"));
-        Akonadi::CollectionCreateJob *create = new Akonadi::CollectionCreateJob(baseCol);
-        AKVERIFYEXEC(create);
-        baseCol = create->collection();
-    }
-
-    {
-        Akonadi::Collection col;
-        col.setParentCollection(baseCol);
-        col.setName(QStringLiteral("referenced"));
-        col.setEnabled(false);
-        {
-            Akonadi::CollectionCreateJob *create = new Akonadi::CollectionCreateJob(col);
-            AKVERIFYEXEC(create);
-            CollectionFetchJob *job = new CollectionFetchJob(create->collection(), CollectionFetchJob::Base);
-            AKVERIFYEXEC(job);
-            col = job->collections().first();
-        }
-        {
-            col.setReferenced(true);
-            Akonadi::CollectionModifyJob *modify = new Akonadi::CollectionModifyJob(col);
-            AKVERIFYEXEC(modify);
-            CollectionFetchJob *job = new CollectionFetchJob(col, CollectionFetchJob::Base);
-            AKVERIFYEXEC(job);
-            Akonadi::Collection result = job->collections().first();
-            QCOMPARE(result.enabled(), false);
-            QCOMPARE(result.referenced(), true);
-        }
-        {
-            col.setReferenced(false);
-            Akonadi::CollectionModifyJob *modify = new Akonadi::CollectionModifyJob(col);
-            AKVERIFYEXEC(modify);
-            CollectionFetchJob *job = new CollectionFetchJob(col, CollectionFetchJob::Base);
-            AKVERIFYEXEC(job);
-            Akonadi::Collection result = job->collections().first();
-            QCOMPARE(result.enabled(), false);
-            QCOMPARE(result.referenced(), false);
-        }
-    }
-
-    //Cleanup
-    CollectionDeleteJob *deleteJob = new CollectionDeleteJob(baseCol);
-    AKVERIFYEXEC(deleteJob);
-}
-
-void ReferenceTest::testReferenceFromMultiSession()
-{
-    Akonadi::Collection baseCol;
-    {
-        baseCol.setParentCollection(Akonadi::Collection(res1ColId));
-        baseCol.setName(QStringLiteral("base"));
-        baseCol.setEnabled(false);
-        Akonadi::CollectionCreateJob *create = new Akonadi::CollectionCreateJob(baseCol);
-        AKVERIFYEXEC(create);
-        baseCol = create->collection();
-    }
-
-    {
-        Akonadi::Collection col;
-        col.setParentCollection(baseCol);
-        col.setName(QStringLiteral("referenced"));
-        col.setEnabled(false);
-        {
-            Akonadi::CollectionCreateJob *create = new Akonadi::CollectionCreateJob(col);
-            AKVERIFYEXEC(create);
-            CollectionFetchJob *job = new CollectionFetchJob(create->collection(), CollectionFetchJob::Base);
-            AKVERIFYEXEC(job);
-            col = job->collections().first();
-        }
-
-        Akonadi::Session *session1 = new Akonadi::Session("session1");
-        Akonadi::Monitor *monitor1 = new Akonadi::Monitor();
-        monitor1->setSession(session1);
-        monitor1->setCollectionMonitored(Collection::root());
-
-        Akonadi::Session *session2 = new Akonadi::Session("session2");
-        Akonadi::Monitor *monitor2 = new Akonadi::Monitor();
-        monitor2->setSession(session2);
-        monitor2->setCollectionMonitored(Collection::root());
-
-        //Reference in first session and ensure second session is not affected
-        {
-            QSignalSpy cmodspy1(monitor1, SIGNAL(collectionChanged(Akonadi::Collection,QSet<QByteArray>)));
-            QSignalSpy cmodspy2(monitor2, SIGNAL(collectionChanged(Akonadi::Collection,QSet<QByteArray>)));
-
-            col.setReferenced(true);
-            Akonadi::CollectionModifyJob *modify = new Akonadi::CollectionModifyJob(col, session1);
-            AKVERIFYEXEC(modify);
-
-            //We want a signal only in the session that referenced the collection
-            QSignalSpy spyMonitor1(monitor1, SIGNAL(collectionChanged(Akonadi::Collection)));
-            QVERIFY(spyMonitor1.wait());
-
-            QTest::qWait(100);
-            QCOMPARE(cmodspy1.count(), 1);
-            QCOMPARE(cmodspy2.count(), 0);
-
-            {
-                CollectionFetchJob *job = new CollectionFetchJob(baseCol, CollectionFetchJob::Recursive, session1);
-                job->fetchScope().setListFilter(CollectionFetchScope::Display);
-                AKVERIFYEXEC(job);
-                QCOMPARE(job->collections().size(), 1);
-            }
-
-            {
-                CollectionFetchJob *job = new CollectionFetchJob(baseCol, CollectionFetchJob::Recursive, session2);
-                job->fetchScope().setListFilter(CollectionFetchScope::Display);
-                AKVERIFYEXEC(job);
-                QCOMPARE(job->collections().size(), 0);
-            }
-        }
-        //Reference in second session and ensure first session is not affected
-        {
-            QSignalSpy cmodspy1(monitor1, SIGNAL(collectionChanged(Akonadi::Collection,QSet<QByteArray>)));
-            QSignalSpy cmodspy2(monitor2, SIGNAL(collectionChanged(Akonadi::Collection,QSet<QByteArray>)));
-
-            col.setReferenced(true);
-            Akonadi::CollectionModifyJob *modify = new Akonadi::CollectionModifyJob(col, session2);
-            AKVERIFYEXEC(modify);
-
-            //We want a signal only in the session that referenced the collection
-            QSignalSpy spyMonitor2(monitor2, SIGNAL(collectionChanged(Akonadi::Collection)));
-            QVERIFY(spyMonitor2.wait());
-
-            QTest::qWait(100);
-            //FIXME The first session still gets the notification since it has the session referenced
-            QCOMPARE(cmodspy1.count(), 1);
-            QCOMPARE(cmodspy2.count(), 1);
-
-            {
-                CollectionFetchJob *job = new CollectionFetchJob(baseCol, CollectionFetchJob::Recursive, session1);
-                job->fetchScope().setListFilter(CollectionFetchScope::Display);
-                AKVERIFYEXEC(job);
-                QCOMPARE(job->collections().size(), 1);
-            }
-
-            {
-                CollectionFetchJob *job = new CollectionFetchJob(baseCol, CollectionFetchJob::Recursive, session2);
-                job->fetchScope().setListFilter(CollectionFetchScope::Display);
-                AKVERIFYEXEC(job);
-                QCOMPARE(job->collections().size(), 1);
-            }
-        }
-        {
-            QSignalSpy cmodspy1(monitor1, SIGNAL(collectionChanged(Akonadi::Collection,QSet<QByteArray>)));
-            QSignalSpy cmodspy2(monitor2, SIGNAL(collectionChanged(Akonadi::Collection,QSet<QByteArray>)));
-            col.setReferenced(false);
-            Akonadi::CollectionModifyJob *modify = new Akonadi::CollectionModifyJob(col, session1);
-            AKVERIFYEXEC(modify);
-
-            //We want a signal only in the session that referenced the collection
-            QSignalSpy spyMonitor1(monitor1, SIGNAL(collectionChanged(Akonadi::Collection)));
-            QVERIFY(spyMonitor1.wait());
-
-            QTest::qWait(100);
-            QCOMPARE(cmodspy1.count(), 1);
-            //FIXME here we still get a notification for dereferenced because we don't filter correctly
-            QCOMPARE(cmodspy2.count(), 1);
-
-            {
-                CollectionFetchJob *job = new CollectionFetchJob(baseCol, CollectionFetchJob::Recursive, session1);
-                job->fetchScope().setListFilter(CollectionFetchScope::Display);
-                AKVERIFYEXEC(job);
-                QCOMPARE(job->collections().size(), 0);
-            }
-
-            {
-                CollectionFetchJob *job = new CollectionFetchJob(baseCol, CollectionFetchJob::Recursive, session2);
-                job->fetchScope().setListFilter(CollectionFetchScope::Display);
-                AKVERIFYEXEC(job);
-                QCOMPARE(job->collections().size(), 1);
-            }
-        }
-    }
-
-    //Cleanup
-    CollectionDeleteJob *deleteJob = new CollectionDeleteJob(baseCol);
-    AKVERIFYEXEC(deleteJob);
-}
diff --git a/autotests/server/CMakeLists.txt b/autotests/server/CMakeLists.txt
--- a/autotests/server/CMakeLists.txt
+++ b/autotests/server/CMakeLists.txt
@@ -101,7 +101,6 @@
 add_server_test(collectioncreatehandlertest.cpp)
 add_server_test(collectionfetchhandlertest.cpp)
 add_server_test(collectionmodifyhandlertest.cpp)
-add_server_test(collectionreferencetest.cpp)
 add_server_test(searchtest.cpp akonadiprivate)
 add_server_test(relationhandlertest.cpp akonadiprivate)
 add_server_test(taghandlertest.cpp akonadiprivate)
diff --git a/autotests/server/collectionreferencetest.cpp b/autotests/server/collectionreferencetest.cpp
deleted file mode 100644
--- a/autotests/server/collectionreferencetest.cpp
+++ /dev/null
@@ -1,264 +0,0 @@
-/*
-    Copyright (c) 2014 Christian Mollekopf <mollekopf@kolabsys.com>
-
-    This library is free software; you can redistribute it and/or modify it
-    under the terms of the GNU Library General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or (at your
-    option) any later version.
-
-    This library is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
-    License for more details.
-
-    You should have received a copy of the GNU Library General Public License
-    along with this library; see the file COPYING.LIB.  If not, write to the
-    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-    02110-1301, USA.
-*/
-#include <QObject>
-
-#include <storage/entity.h>
-
-#include "fakeakonadiserver.h"
-#include "fakedatastore.h"
-#include <shared/aktest.h>
-#include "entities.h"
-#include "collectionreferencemanager.h"
-#include "dbinitializer.h"
-
-#include <private/scope_p.h>
-
-#include <QTest>
-
-using namespace Akonadi;
-using namespace Akonadi::Server;
-
-Q_DECLARE_METATYPE(Collection::List)
-
-class CollectionReferenceTest : public QObject
-{
-    Q_OBJECT
-
-    DbInitializer initializer;
-
-public:
-    CollectionReferenceTest()
-    {
-        FakeAkonadiServer::instance()->setPopulateDb(false);
-        FakeAkonadiServer::instance()->init();
-
-        initializer.createResource("testresource");
-        initializer.createCollection("col1");
-        Collection col2 = initializer.createCollection("col2");
-        col2.setEnabled(false);
-        col2.update();
-    }
-
-    ~CollectionReferenceTest()
-    {
-        FakeAkonadiServer::instance()->quit();
-    }
-
-private Q_SLOTS:
-    void testModify_data()
-    {
-        QTest::addColumn<TestScenario::List>("scenarios");
-        QTest::addColumn<Protocol::ChangeNotificationList>("expectedNotifications");
-
-        auto notificationTemplate = Protocol::CollectionChangeNotificationPtr::create();
-        notificationTemplate->setOperation(Protocol::CollectionChangeNotification::Modify);
-        notificationTemplate->setParentCollection(0);
-        notificationTemplate->setResource("testresource");
-        notificationTemplate->setSessionId(FakeAkonadiServer::instanceName().toLatin1());
-        Protocol::FetchCollectionsResponse collection;
-        collection.setId(initializer.collection("col2").id());
-        collection.setRemoteId(QStringLiteral("col2"));
-        collection.setRemoteRevision(QStringLiteral(""));
-        notificationTemplate->setCollection(std::move(collection));
-
-        {
-            auto cmd = Protocol::FetchCollectionsCommandPtr::create();
-            cmd->setDepth(Protocol::FetchCollectionsCommand::AllCollections);
-            cmd->setResource(QStringLiteral("testresource"));
-            cmd->setEnabled(true);
-
-            TestScenario::List scenarios;
-            scenarios << FakeAkonadiServer::loginScenario()
-                      << TestScenario::create(5, TestScenario::ClientCmd, cmd)
-                      << TestScenario::create(5, TestScenario::ServerCmd, initializer.listResponse(initializer.collection("col1")))
-                      << TestScenario::create(5, TestScenario::ServerCmd, Protocol::FetchCollectionsResponsePtr::create());
-            QTest::newRow("list before referenced first level") << scenarios << Protocol::ChangeNotificationList();
-        }
-
-        {
-            auto cmd = Protocol::ModifyCollectionCommandPtr::create(initializer.collection("col2").id());
-            cmd->setReferenced(true);
-
-            TestScenario::List scenarios;
-            scenarios << FakeAkonadiServer::loginScenario()
-                      << TestScenario::create(5, TestScenario::ClientCmd, cmd)
-                      << TestScenario::create(5, TestScenario::ServerCmd, Protocol::ModifyCollectionResponsePtr::create());
-
-            auto notification = Protocol::CollectionChangeNotificationPtr::create(*notificationTemplate);
-            notification->setChangedParts(QSet<QByteArray>() << "REFERENCED");
-
-            QTest::newRow("reference") << scenarios << (Protocol::ChangeNotificationList() << notification);
-        }
-
-        {
-            auto cmd = Protocol::ModifyCollectionCommandPtr::create(initializer.collection("col2").id());
-            cmd->setReferenced(true);
-
-            auto listCmd = Protocol::FetchCollectionsCommandPtr::create(initializer.collection("col2").id());
-            listCmd->setDepth(Protocol::FetchCollectionsCommand::BaseCollection);
-            listCmd->setEnabled(true);
-
-            Collection col2 = initializer.collection("col2");
-            col2.setReferenced(true);
-            TestScenario::List scenarios;
-            scenarios << FakeAkonadiServer::loginScenario()
-                      << TestScenario::create(5, TestScenario::ClientCmd, cmd)
-                      << TestScenario::create(5, TestScenario::ServerCmd, Protocol::ModifyCollectionResponsePtr::create())
-                      << TestScenario::create(6, TestScenario::ClientCmd, listCmd)
-                      << TestScenario::create(6, TestScenario::ServerCmd, initializer.listResponse(col2))
-                      << TestScenario::create(6, TestScenario::ServerCmd, Protocol::FetchCollectionsResponsePtr::create());
-
-            auto notification = Protocol::CollectionChangeNotificationPtr::create(*notificationTemplate);
-            notification->setChangedParts(QSet<QByteArray>() << "REFERENCED");
-
-            QTest::newRow("list referenced base") << scenarios << (Protocol::ChangeNotificationList() << notification);
-        }
-        {
-            auto cmd = Protocol::ModifyCollectionCommandPtr::create(initializer.collection("col2").id());
-            cmd->setReferenced(true);
-
-            auto listCmd = Protocol::FetchCollectionsCommandPtr::create();
-            listCmd->setResource(QStringLiteral("testresource"));
-            listCmd->setEnabled(true);
-            listCmd->setDepth(Protocol::FetchCollectionsCommand::ParentCollection);
-
-            Collection col2 = initializer.collection("col2");
-            col2.setReferenced(true);
-            TestScenario::List scenarios;
-            scenarios << FakeAkonadiServer::loginScenario()
-                      << TestScenario::create(5, TestScenario::ClientCmd, cmd)
-                      << TestScenario::create(5, TestScenario::ServerCmd, Protocol::ModifyCollectionResponsePtr::create())
-                      << TestScenario::create(6, TestScenario::ClientCmd, listCmd)
-                      << TestScenario::create(6, TestScenario::ServerCmd, initializer.listResponse(initializer.collection("col1")))
-                      << TestScenario::create(6, TestScenario::ServerCmd, initializer.listResponse(col2))
-                      << TestScenario::create(6, TestScenario::ServerCmd, Protocol::FetchCollectionsResponsePtr::create());
-
-            auto notification = Protocol::CollectionChangeNotificationPtr::create(*notificationTemplate);
-            notification->setChangedParts(QSet<QByteArray>() << "REFERENCED");
-
-            QTest::newRow("list referenced first level") << scenarios << (Protocol::ChangeNotificationList() << notification);
-        }
-        {
-            auto cmd1 = Protocol::ModifyCollectionCommandPtr::create(initializer.collection("col2").id());
-            cmd1->setReferenced(true);
-
-            auto cmd2 = Protocol::ModifyCollectionCommandPtr::create(initializer.collection("col2").id());
-            cmd2->setReferenced(false);
-
-            TestScenario::List scenarios;
-            scenarios << FakeAkonadiServer::loginScenario()
-                      << TestScenario::create(5, TestScenario::ClientCmd, cmd1)
-                      << TestScenario::create(5, TestScenario::ServerCmd, Protocol::ModifyCollectionResponsePtr::create())
-                      << TestScenario::create(6, TestScenario::ClientCmd, cmd2)
-                      << TestScenario::create(6, TestScenario::ServerCmd, Protocol::ModifyCollectionResponsePtr::create());
-
-            auto notification = Protocol::CollectionChangeNotificationPtr::create(*notificationTemplate);
-            notification->setChangedParts(QSet<QByteArray>() << "REFERENCED");
-
-            QTest::newRow("dereference") << scenarios << (Protocol::ChangeNotificationList() << notification << notification);
-        }
-    }
-
-    void testModify()
-    {
-        QFETCH(TestScenario::List, scenarios);
-        QFETCH(Protocol::ChangeNotificationList, expectedNotifications);
-
-        // Clean all references from previous run
-        CollectionReferenceManager::cleanup();
-
-        FakeAkonadiServer::instance()->setScenarios(scenarios);
-        FakeAkonadiServer::instance()->runTest();
-
-        auto notificationSpy = FakeAkonadiServer::instance()->notificationSpy();
-        if (expectedNotifications.isEmpty()) {
-            QTRY_VERIFY(notificationSpy->isEmpty() || notificationSpy->takeFirst().first().value<Protocol::ChangeNotificationList>().isEmpty());
-        } else {
-            Protocol::ChangeNotificationList receivedNotifications;
-            for (int q = 0; q < notificationSpy->size(); q++) {
-                //Only one notify call
-                QCOMPARE(notificationSpy->first().count(), 1);
-                const Protocol::ChangeNotificationList n = notificationSpy->first().first().value<Protocol::ChangeNotificationList>();
-                for (int i = 0; i < n.size(); i++) {
-                    receivedNotifications.append(n.at(i));
-                }
-            }
-            QCOMPARE(receivedNotifications.size(), expectedNotifications.count());
-            for (int i = 0; i < expectedNotifications.size(); i++) {
-                QCOMPARE(*receivedNotifications.at(i), *expectedNotifications.at(i));
-            }
-        }
-    }
-
-    void testReferenceCollection()
-    {
-        Collection col = initializer.createCollection("testReferenceCollection");
-
-        CollectionReferenceManager::instance()->referenceCollection("testReferenceCollectionSession", col, true);
-        QVERIFY(CollectionReferenceManager::instance()->isReferenced(col.id()));
-        QVERIFY(CollectionReferenceManager::instance()->isReferenced(col.id(), "testReferenceCollectionSession"));
-
-        CollectionReferenceManager::instance()->referenceCollection("foobar", col, false);
-        QVERIFY(CollectionReferenceManager::instance()->isReferenced(col.id()));
-        QVERIFY(CollectionReferenceManager::instance()->isReferenced(col.id(), "testReferenceCollectionSession"));
-
-        CollectionReferenceManager::instance()->referenceCollection("testReferenceCollectionSession", col, false);
-        QVERIFY(!CollectionReferenceManager::instance()->isReferenced(col.id()));
-        QVERIFY(!CollectionReferenceManager::instance()->isReferenced(col.id(), "testReferenceCollectionSession"));
-        QVERIFY(col.remove());
-    }
-
-    void testSessionClosed()
-    {
-        Collection col = initializer.createCollection("testSessionCollection");
-        col.setReferenced(true);
-        QVERIFY(col.update());
-        CollectionReferenceManager::instance()->referenceCollection("testSessionClosedSession", col, true);
-        CollectionReferenceManager::instance()->referenceCollection("testSessionClosedSession2", col, true);
-
-        //Remove first session
-        CollectionReferenceManager::instance()->removeSession("testSessionClosedSession2");
-        QVERIFY(Collection::retrieveById(col.id()).referenced());
-        QVERIFY(!CollectionReferenceManager::instance()->isReferenced(col.id(), "testSessionClosedSession2"));
-        QVERIFY(CollectionReferenceManager::instance()->isReferenced(col.id(), "testSessionClosedSession"));
-
-        CollectionReferenceManager::instance()->removeSession("testSessionClosedSession");
-        QVERIFY(!Collection::retrieveById(col.id()).referenced());
-        QVERIFY(!CollectionReferenceManager::instance()->isReferenced(col.id(), "testSessionClosedSession"));
-
-        QVERIFY(col.remove());
-    }
-
-    void testCleanup()
-    {
-        Collection col = initializer.createCollection("testCleanupCollection");
-        col.setReferenced(true);
-        QVERIFY(col.update());
-
-        CollectionReferenceManager::cleanup();
-        QVERIFY(!Collection::retrieveById(col.id()).referenced());
-
-        QVERIFY(col.remove());
-    }
-
-};
-
-AKTEST_FAKESERVER_MAIN(CollectionReferenceTest)
-
-#include "collectionreferencetest.moc"
diff --git a/autotests/server/dbinitializer.cpp b/autotests/server/dbinitializer.cpp
--- a/autotests/server/dbinitializer.cpp
+++ b/autotests/server/dbinitializer.cpp
@@ -165,7 +165,6 @@
         ancs.push_back(Akonadi::Protocol::Ancestor(0));
         resp->setAncestors(ancs);
     }
-    resp->setReferenced(col.referenced());
     resp->setEnabled(col.enabled());
     resp->setDisplayPref(static_cast<Tristate>(col.displayPref()));
     resp->setSyncPref(static_cast<Tristate>(col.syncPref()));
diff --git a/src/agentbase/resourcebase.cpp b/src/agentbase/resourcebase.cpp
--- a/src/agentbase/resourcebase.cpp
+++ b/src/agentbase/resourcebase.cpp
@@ -1312,7 +1312,7 @@
         const Collection::List list = static_cast<CollectionFetchJob *>(job)->collections();
         for (const Collection &collection : list) {
             //We also get collections that should not be synced but are part of the tree.
-            if (collection.shouldList(Collection::ListSync) || collection.referenced()) {
+            if (collection.shouldList(Collection::ListSync)) {
                 if (mScheduleAttributeSyncBeforeCollectionSync) {
                     scheduler->scheduleAttributesSync(collection);
                 }
diff --git a/src/core/changerecorderjournal.cpp b/src/core/changerecorderjournal.cpp
--- a/src/core/changerecorderjournal.cpp
+++ b/src/core/changerecorderjournal.cpp
@@ -623,8 +623,7 @@
             collection.setSyncPref(tristate);
             stream >> reinterpret_cast<qint8&>(tristate);
             collection.setIndexPref(tristate);
-            stream >> b;
-            collection.setReferenced(b);
+            stream >> b; // read the deprecated "isReferenced" value
             stream >> b;
             collection.setIsVirtual(b);
 
@@ -716,7 +715,7 @@
     stream << static_cast<qint8>(col.displayPref());
     stream << static_cast<qint8>(col.syncPref());
     stream << static_cast<qint8>(col.indexPref());
-    stream << col.referenced();
+    stream << false; // write the deprecated "isReferenced" value
     stream << col.isVirtual();
 
 
diff --git a/src/core/collection.h b/src/core/collection.h
--- a/src/core/collection.h
+++ b/src/core/collection.h
@@ -520,24 +520,6 @@
      */
     void setShouldList(ListPurpose purpose, bool shouldList);
 
-    /**
-     * Sets a collection to be referenced.
-     *
-     * A referenced collection is temporarily shown and synchronized even when disabled.
-     * A reference is only valid for the duration of a session, and is automatically removed afterwards.
-     *
-     * Referenced collections are only visible if explicitly monitored in the ETM.
-     *
-     * @since 4.14
-     */
-    void setReferenced(bool referenced);
-
-    /**
-     * Returns the referenced state of the collection.
-     * @since 4.14
-     */
-    Q_REQUIRED_RESULT bool referenced() const;
-
     /**
      * Set during sync to indicate that the provided parts are only default values;
      * @since 4.15
diff --git a/src/core/collection.cpp b/src/core/collection.cpp
--- a/src/core/collection.cpp
+++ b/src/core/collection.cpp
@@ -415,7 +415,7 @@
 bool Collection::shouldList(Collection::ListPurpose purpose) const
 {
     if (localListPreference(purpose) == ListDefault) {
-        return enabled() || referenced();
+        return enabled();
     }
     return (localListPreference(purpose) == ListEnabled);
 }
@@ -429,17 +429,6 @@
     }
 }
 
-void Collection::setReferenced(bool referenced)
-{
-    d_ptr->referencedChanged = true;
-    d_ptr->referenced = referenced;
-}
-
-bool Collection::referenced() const
-{
-    return d_ptr->referenced;
-}
-
 void Collection::setKeepLocalChanges(const QSet<QByteArray> &parts)
 {
     d_ptr->keepLocalChanges = parts;
diff --git a/src/core/collection_p.h b/src/core/collection_p.h
--- a/src/core/collection_p.h
+++ b/src/core/collection_p.h
@@ -45,8 +45,6 @@
         , listPreferenceChanged(false)
         , enabled(true)
         , enabledChanged(false)
-        , referenced(false)
-        , referencedChanged(false)
         , contentTypesChanged(false)
         , cachePolicyChanged(false)
         , isVirtual(false)
@@ -80,8 +78,6 @@
         syncPreference = other.syncPreference;
         indexPreference = other.indexPreference;
         listPreferenceChanged = other.listPreferenceChanged;
-        referenced = other.referenced;
-        referencedChanged = other.referencedChanged;
         keepLocalChanges = other.keepLocalChanges;
     }
 
@@ -96,7 +92,6 @@
         cachePolicyChanged = false;
         enabledChanged = false;
         listPreferenceChanged = false;
-        referencedChanged = false;
         mAttributeStorage.resetChangeLog();
     }
 
@@ -114,8 +109,6 @@
     bool listPreferenceChanged: 1;
     bool enabled: 1;
     bool enabledChanged: 1;
-    bool referenced: 1;
-    bool referencedChanged: 1;
     bool contentTypesChanged: 1;
     bool cachePolicyChanged: 1;
     bool isVirtual: 1;
diff --git a/src/core/jobs/collectionmodifyjob.cpp b/src/core/jobs/collectionmodifyjob.cpp
--- a/src/core/jobs/collectionmodifyjob.cpp
+++ b/src/core/jobs/collectionmodifyjob.cpp
@@ -97,9 +97,6 @@
         cmd->setSyncPref(ProtocolHelper::listPreference(d->mCollection.localListPreference(Collection::ListSync)));
         cmd->setIndexPref(ProtocolHelper::listPreference(d->mCollection.localListPreference(Collection::ListIndex)));
     }
-    if (d->mCollection.d_ptr->referencedChanged) {
-        cmd->setReferenced(d->mCollection.referenced());
-    }
     if (d->mCollection.d_ptr->mAttributeStorage.hasModifiedAttributes()) {
         cmd->setAttributes(ProtocolHelper::attributesToProtocol(d->mCollection.d_ptr->mAttributeStorage.modifiedAttributes()));
     }
diff --git a/src/core/models/entitytreemodel.h b/src/core/models/entitytreemodel.h
--- a/src/core/models/entitytreemodel.h
+++ b/src/core/models/entitytreemodel.h
@@ -451,15 +451,6 @@
      */
     void setCollectionMonitored(const Akonadi::Collection &col, bool monitored = true);
 
-    /**
-     * References a collection and starts to monitor it.
-     *
-     * Use this to temporarily include a collection that is not enabled.
-     *
-     * @since 4.14
-     */
-    void setCollectionReferenced(const Akonadi::Collection &col, bool referenced = true);
-
     /**
      * Sets the item population @p strategy of the model.
      */
diff --git a/src/core/models/entitytreemodel.cpp b/src/core/models/entitytreemodel.cpp
--- a/src/core/models/entitytreemodel.cpp
+++ b/src/core/models/entitytreemodel.cpp
@@ -114,15 +114,6 @@
     d->m_monitor->setCollectionMonitored(col, monitored);
 }
 
-void EntityTreeModel::setCollectionReferenced(const Akonadi::Collection &col, bool referenced)
-{
-    Q_D(EntityTreeModel);
-    Akonadi::Collection referencedCollection = col;
-    referencedCollection.setReferenced(referenced);
-    //We have to use the same session as the monitor, so the monitor can fetch the collection afterwards
-    new Akonadi::CollectionModifyJob(referencedCollection, d->m_monitor->session());
-}
-
 bool EntityTreeModel::systemEntitiesShown() const
 {
     Q_D(const EntityTreeModel);
diff --git a/src/core/models/entitytreemodel_p.cpp b/src/core/models/entitytreemodel_p.cpp
--- a/src/core/models/entitytreemodel_p.cpp
+++ b/src/core/models/entitytreemodel_p.cpp
@@ -789,7 +789,7 @@
     }
 
     if (m_listFilter == CollectionFetchScope::Enabled) {
-        if (!collection.enabled() && !collection.referenced()) {
+        if (!collection.enabled()) {
             return false;
         }
     } else if (m_listFilter == CollectionFetchScope::Display) {
diff --git a/src/core/protocolhelper.cpp b/src/core/protocolhelper.cpp
--- a/src/core/protocolhelper.cpp
+++ b/src/core/protocolhelper.cpp
@@ -237,7 +237,6 @@
     collection.setLocalListPreference(Collection::ListDisplay, parsePreference(data.displayPref()));
     collection.setLocalListPreference(Collection::ListIndex, parsePreference(data.indexPref()));
     collection.setLocalListPreference(Collection::ListSync, parsePreference(data.syncPref()));
-    collection.setReferenced(data.referenced());
 
     if (!data.searchQuery().isEmpty()) {
         auto attr = collection.attribute<PersistentSearchAttribute>(Collection::AddIfMissing);
diff --git a/src/private/protocol.xml b/src/private/protocol.xml
--- a/src/private/protocol.xml
+++ b/src/private/protocol.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<protocol version="61">
+<protocol version="62">
 
   <class name="Ancestor">
     <enum name="Depth">
@@ -531,7 +531,6 @@
     <param name="displayPref" type="Tristate" default="Tristate::Undefined" />
     <param name="syncPref" type="Tristate" default="Tristate::Undefined" />
     <param name="indexPref" type="Tristate" default="Tristate::Undefined" />
-    <param name="referenced" type="bool" />
     <param name="isVirtual" type="bool" />
   </response>
 
@@ -550,7 +549,6 @@
       <value name="RemovedAttributes" value="128" />
       <value name="Attributes" value="256" />
       <value name="ListPreferences" value="512" />
-      <value name="Referenced" value="1024" />
     </flag>
 
     <ctor>
@@ -607,9 +605,6 @@
     <param name="indexPref" type="Tristate" default="Tristate::Undefined">
       <depends enum="modifiedParts" value="ModifyCollectionCommand::ListPreferences" />
     </param>
-    <param name="referenced" type="bool">
-      <depends enum="modifiedParts" value="ModifyCollectionCommand::Referenced" />
-    </param>
   </command>
 
   <response name="ModifyCollection" />
diff --git a/src/private/protocol_p.h b/src/private/protocol_p.h
--- a/src/private/protocol_p.h
+++ b/src/private/protocol_p.h
@@ -615,7 +615,6 @@
 #define AKONADI_PARAM_PLD                          "PLD:"
 #define AKONADI_PARAM_PLD_RFC822                   "PLD:RFC822"
 #define AKONADI_PARAM_RECURSIVE                    "RECURSIVE"
-#define AKONADI_PARAM_REFERENCED                   "REFERENCED"
 #define AKONADI_PARAM_REMOTE                       "REMOTE"
 #define AKONADI_PARAM_REMOTEID                     "REMOTEID"
 #define AKONADI_PARAM_REMOTEREVISION               "REMOTEREVISION"
diff --git a/src/server/CMakeLists.txt b/src/server/CMakeLists.txt
--- a/src/server/CMakeLists.txt
+++ b/src/server/CMakeLists.txt
@@ -50,7 +50,6 @@
     handler.cpp
     handlerhelper.cpp
     intervalcheck.cpp
-    collectionreferencemanager.cpp
     handler/collectioncopyhandler.cpp
     handler/collectioncreatehandler.cpp
     handler/collectiondeletehandler.cpp
diff --git a/src/server/akonadi.cpp b/src/server/akonadi.cpp
--- a/src/server/akonadi.cpp
+++ b/src/server/akonadi.cpp
@@ -40,8 +40,6 @@
 #include "search/searchtaskmanager.h"
 #include "aklocalserver.h"
 
-#include "collectionreferencemanager.h"
-
 #include <private/standarddirs_p.h>
 #include <private/protocol_p.h>
 #include <private/dbus_p.h>
@@ -227,9 +225,6 @@
     // operation was interrupted...
     db->unhideAllPimItems();
 
-    // Cleanup referenced collections from the last run
-    CollectionReferenceManager::cleanup();
-
     // We are ready, now register org.freedesktop.Akonadi service to DBus and
     // the fun can begin
     if (!QDBusConnection::sessionBus().registerService(DBus::serviceName(DBus::Server))) {
diff --git a/src/server/collectionreferencemanager.h b/src/server/collectionreferencemanager.h
deleted file mode 100644
--- a/src/server/collectionreferencemanager.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
-    Copyright (c) 2014 Christian Mollekopf <mollekopf@kolabsys.com>
-
-    This library is free software; you can redistribute it and/or modify it
-    under the terms of the GNU Library General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or (at your
-    option) any later version.
-
-    This library is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
-    License for more details.
-
-    You should have received a copy of the GNU Library General Public License
-    along with this library; see the file COPYING.LIB.  If not, write to the
-    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-    02110-1301, USA.
-*/
-#ifndef COLLECTIONREFERENCEMANAGER_H
-#define COLLECTIONREFERENCEMANAGER_H
-
-#include "storage/entity.h"
-#include "entities.h"
-#include <QMutex>
-
-namespace Akonadi
-{
-namespace Server
-{
-
-class CollectionReferenceManager
-{
-public:
-    static CollectionReferenceManager *instance();
-
-    void referenceCollection(const QByteArray &sessionId, const Collection &collection, bool reference);
-    void removeSession(const QByteArray &sessionId);
-    bool isReferenced(Collection::Id collection) const;
-    bool isReferenced(Collection::Id collection, const QByteArray &sessionId) const;
-
-    static void cleanup();
-
-private:
-    CollectionReferenceManager();
-    void expireCollectionIfNecessary(Collection::Id collection);
-
-    QMultiHash<Collection::Id, QByteArray> mReferenceMap;
-    static CollectionReferenceManager *s_instance;
-    mutable QMutex mReferenceLock;
-};
-
-}
-}
-
-#endif
diff --git a/src/server/collectionreferencemanager.cpp b/src/server/collectionreferencemanager.cpp
deleted file mode 100644
--- a/src/server/collectionreferencemanager.cpp
+++ /dev/null
@@ -1,114 +0,0 @@
-/*
-    Copyright (c) 2014 Christian Mollekopf <mollekopf@kolabsys.com>
-
-    This library is free software; you can redistribute it and/or modify it
-    under the terms of the GNU Library General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or (at your
-    option) any later version.
-
-    This library is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
-    License for more details.
-
-    You should have received a copy of the GNU Library General Public License
-    along with this library; see the file COPYING.LIB.  If not, write to the
-    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-    02110-1301, USA.
-*/
-
-#include "collectionreferencemanager.h"
-#include "akonadi.h"
-#include "akonadiserver_debug.h"
-#include "cachecleaner.h"
-#include "storage/selectquerybuilder.h"
-
-using namespace Akonadi;
-using namespace Akonadi::Server;
-
-CollectionReferenceManager *CollectionReferenceManager::s_instance = nullptr;
-
-CollectionReferenceManager::CollectionReferenceManager()
-    : mReferenceLock(QMutex::Recursive)
-{
-}
-
-CollectionReferenceManager *CollectionReferenceManager::instance()
-{
-    static QMutex s_instanceLock;
-    QMutexLocker locker(&s_instanceLock);
-    if (!s_instance) {
-        s_instance = new CollectionReferenceManager();
-    }
-    return s_instance;
-}
-
-void CollectionReferenceManager::referenceCollection(const QByteArray &sessionId, const Collection &collection, bool reference)
-{
-    QMutexLocker locker(&mReferenceLock);
-    if (reference) {
-        if (!mReferenceMap.contains(collection.id(), sessionId)) {
-            mReferenceMap.insert(collection.id(), sessionId);
-        }
-    } else {
-        mReferenceMap.remove(collection.id(), sessionId);
-        expireCollectionIfNecessary(collection.id());
-    }
-}
-
-void CollectionReferenceManager::removeSession(const QByteArray &sessionId)
-{
-    QMutexLocker locker(&mReferenceLock);
-    const QList<Collection::Id> lstCol = mReferenceMap.keys(sessionId);
-    for (Collection::Id col : lstCol ) {
-        mReferenceMap.remove(col, sessionId);
-        expireCollectionIfNecessary(col);
-        if (!isReferenced(col)) {
-            Collection collection = Collection::retrieveById(col);
-            collection.setReferenced(false);
-            collection.update();
-        }
-    }
-}
-
-bool CollectionReferenceManager::isReferenced(Collection::Id collection) const
-{
-    QMutexLocker locker(&mReferenceLock);
-    return mReferenceMap.contains(collection);
-}
-
-bool CollectionReferenceManager::isReferenced(Collection::Id collection, const QByteArray &sessionId) const
-{
-    QMutexLocker locker(&mReferenceLock);
-    return mReferenceMap.contains(collection, sessionId);
-}
-
-void CollectionReferenceManager::expireCollectionIfNecessary(Collection::Id collection)
-{
-    QMutexLocker locker(&mReferenceLock);
-    if (!isReferenced(collection)) {
-        if (AkonadiServer::instance()->cacheCleaner()) {
-            AkonadiServer::instance()->cacheCleaner()->collectionChanged(collection);
-        }
-    }
-}
-
-void CollectionReferenceManager::cleanup()
-{
-    SelectQueryBuilder<Collection> qb;
-    qb.addValueCondition(Collection::referencedColumn(), Query::Equals, true);
-    if (!qb.exec()) {
-        qCCritical(AKONADISERVER_LOG) << "Failed to execute  collection reference cleanup query.";
-        return;
-    }
-    const QVector<Collection> colVect = qb.result();
-    for (Collection col : colVect) {
-        col.setReferenced(false);
-        col.update();
-        if (AkonadiServer::instance()->cacheCleaner()) {
-            AkonadiServer::instance()->cacheCleaner()->collectionChanged(col.id());
-        }
-    }
-    QMutexLocker locker(&instance()->mReferenceLock);
-    instance()->mReferenceMap.clear();
-}
diff --git a/src/server/collectionscheduler.cpp b/src/server/collectionscheduler.cpp
--- a/src/server/collectionscheduler.cpp
+++ b/src/server/collectionscheduler.cpp
@@ -301,7 +301,6 @@
     andCondition.addValueCondition(Collection::syncPrefFullColumnName(), Query::Equals, (int)Akonadi::Tristate::Undefined);
     andCondition.addValueCondition(Collection::enabledFullColumnName(), Query::Equals, true);
     orCondition.addCondition(andCondition);
-    orCondition.addValueCondition(Collection::referencedFullColumnName(), Query::Equals, true);
     qb.addCondition(orCondition);
     if (!qb.exec()) {
         qCWarning(AKONADISERVER_LOG) << "Failed to query initial collections for scheduler!";
diff --git a/src/server/connection.h b/src/server/connection.h
--- a/src/server/connection.h
+++ b/src/server/connection.h
@@ -46,7 +46,6 @@
 class Response;
 class DataStore;
 class Collection;
-class CollectionReferenceManager;
 
 /**
     An Connection represents one connection of a client to the server.
@@ -60,8 +59,6 @@
 
     virtual DataStore *storageBackend();
 
-    CollectionReferenceManager *collectionReferenceManager();
-
     CommandContext *context() const;
 
     /**
diff --git a/src/server/connection.cpp b/src/server/connection.cpp
--- a/src/server/connection.cpp
+++ b/src/server/connection.cpp
@@ -33,7 +33,6 @@
 #include "notificationmanager.h"
 
 #include "tracer.h"
-#include "collectionreferencemanager.h"
 
 #include <cassert>
 
@@ -121,7 +120,6 @@
     }
 
     Tracer::self()->endConnection(m_identifier, QString());
-    collectionReferenceManager()->removeSession(m_sessionId);
 
     delete m_socket;
     m_socket = nullptr;
@@ -154,11 +152,6 @@
     return m_backend;
 }
 
-CollectionReferenceManager *Connection::collectionReferenceManager()
-{
-    return CollectionReferenceManager::instance();
-}
-
 Connection::~Connection()
 {
     quitThread();
diff --git a/src/server/handler/collectionfetchhandler.cpp b/src/server/handler/collectionfetchhandler.cpp
--- a/src/server/handler/collectionfetchhandler.cpp
+++ b/src/server/handler/collectionfetchhandler.cpp
@@ -23,7 +23,6 @@
 
 #include "connection.h"
 #include "handlerhelper.h"
-#include "collectionreferencemanager.h"
 #include "storage/datastore.h"
 #include "storage/selectquerybuilder.h"
 #include "storage/collectionqueryhelper.h"
@@ -82,15 +81,6 @@
         ++it;
     }
 
-    // We need the reference and enabled status, to not need to request the server multiple times.
-    // Mostly interesting for ancestors for i.e. updates provided by the monitor.
-    const bool isReferenced = connection()->collectionReferenceManager()->isReferenced(col.id(), connection()->sessionId());
-    if (isReferenced) {
-        CollectionAttribute attr;
-        attr.setType(AKONADI_PARAM_REFERENCED);
-        attr.setValue("TRUE");
-        attributes << attr;
-    }
     {
         CollectionAttribute attr;
         attr.setType(AKONADI_PARAM_ENABLED);
@@ -106,11 +96,6 @@
                                             const QStringList &mimeTypes,
                                             const CollectionAttribute::List &attributes)
 {
-    const bool isReferencedFromSession = connection()->collectionReferenceManager()->isReferenced(root.id(), connection()->sessionId());
-    //We always expose referenced collections to the resource as referenced (although it's a different session)
-    //Otherwise syncing wouldn't work.
-    const bool resourceIsSynchronizing = root.referenced() && mCollectionsToSynchronize && connection()->context()->resource().isValid();
-
     QStack<CollectionAttribute::List> ancestorAttributes;
     //backwards compatibility, collectionToByteArray will automatically fall-back to id + remoteid
     if (!mAncestorAttributes.isEmpty()) {
@@ -127,7 +112,6 @@
     sendResponse(HandlerHelper::fetchCollectionsResponse(dummy, attributes, mIncludeStatistics,
                  mAncestorDepth, ancestors,
                  ancestorAttributes,
-                 isReferencedFromSession || resourceIsSynchronizing,
                  mimeTypes));
 }
 
@@ -139,7 +123,6 @@
     andCondition.addValueCondition(column, Query::Equals, (int)Collection::Undefined);
     andCondition.addValueCondition(Collection::enabledFullColumnName(), Query::Equals, true);
     orCondition.addCondition(andCondition);
-    orCondition.addValueCondition(Collection::referencedFullColumnName(), Query::Equals, true);
     return orCondition;
 }
 
@@ -242,7 +225,6 @@
      * * First all collections that match the given criteria are queried
      * * We then filter the false positives:
      * ** all collections out that are not part of the tree we asked for are filtered
-     * ** all collections that are referenced but not by this session or by the owning resource are filtered
      * * Finally we complete the tree by adding missing collections
      *
      * Mimetypes and attributes are also retrieved in single queries to avoid spawning two queries per collection (the N+1 problem).
@@ -279,10 +261,7 @@
             } else if (mCollectionsToIndex) {
                 qb.addCondition(filterCondition(Collection::indexPrefFullColumnName()));
             } else if (mEnabledCollections) {
-                Query::Condition orCondition(Query::Or);
-                orCondition.addValueCondition(Collection::enabledFullColumnName(), Query::Equals, true);
-                orCondition.addValueCondition(Collection::referencedFullColumnName(), Query::Equals, true);
-                qb.addCondition(orCondition);
+                qb.addValueCondition(Collection::enabledFullColumnName(), Query::Equals, true);
             }
             if (mResource.isValid()) {
                 qb.addValueCondition(Collection::resourceIdFullColumnName(), Query::Equals, mResource.id());
@@ -334,19 +313,6 @@
                     continue;
                 }
             }
-
-            //If we matched referenced collections we need to ensure the collection was referenced from this session
-            const bool isReferencedFromSession = connection()->collectionReferenceManager()->isReferenced(it->id(), connection()->sessionId());
-            //The collection is referenced, but not from this session. We need to reevaluate the filter condition
-            if (it->referenced() && !isReferencedFromSession) {
-                //Don't include the collection when only looking for enabled collections.
-                //However, a referenced collection should be still synchronized by the resource, so we exclude this case.
-                if (!checkFilterCondition(*it) && !(mCollectionsToSynchronize && connection()->context()->resource().isValid())) {
-                    it = mCollections.erase(it);
-                    continue;
-                }
-            }
-
             ++it;
         }
     }
diff --git a/src/server/handler/collectionmodifyhandler.cpp b/src/server/handler/collectionmodifyhandler.cpp
--- a/src/server/handler/collectionmodifyhandler.cpp
+++ b/src/server/handler/collectionmodifyhandler.cpp
@@ -23,7 +23,6 @@
 #include "connection.h"
 #include "handlerhelper.h"
 #include "cachecleaner.h"
-#include "collectionreferencemanager.h"
 #include "intervalcheck.h"
 #include "storage/datastore.h"
 #include "storage/transaction.h"
@@ -64,7 +63,6 @@
     DataStore *db = connection()->storageBackend();
     Transaction transaction(db, QStringLiteral("MODIFY"));
     QList<QByteArray> changes;
-    bool referencedChanged = false;
 
     if (cmd.modifiedParts() & Protocol::ModifyCollectionCommand::MimeTypes) {
         QStringList mts = cmd.mimeTypes();
@@ -224,19 +222,6 @@
         }
     }
 
-    if (cmd.modifiedParts() & Protocol::ModifyCollectionCommand::Referenced) {
-        const bool wasReferencedFromSession = connection()->collectionReferenceManager()->isReferenced(collection.id(), connection()->sessionId());
-        connection()->collectionReferenceManager()->referenceCollection(connection()->sessionId(), collection, cmd.referenced());
-        const bool referenced = connection()->collectionReferenceManager()->isReferenced(collection.id());
-        if (cmd.referenced() != wasReferencedFromSession) {
-            changes.append(AKONADI_PARAM_REFERENCED);
-        }
-        if (referenced != collection.referenced()) {
-            referencedChanged = true;
-            collection.setReferenced(referenced);
-        }
-    }
-
     if (cmd.modifiedParts() & Protocol::ModifyCollectionCommand::RemovedAttributes) {
         Q_FOREACH (const QByteArray &attr, cmd.removedAttributes()) {
             if (db->removeCollectionAttribute(collection, attr)) {
@@ -285,10 +270,6 @@
         if (collection.hasPendingChanges() && !collection.update()) {
             return failureResponse("Unable to update collection");
         }
-        //This must be after the collection was updated in the db. The resource will immediately request a copy of the collection.
-        if (AkonadiServer::instance()->intervalChecker() && collection.referenced() && referencedChanged) {
-            AkonadiServer::instance()->intervalChecker()->requestCollectionSync(collection);
-        }
         db->notificationCollector()->collectionChanged(collection, changes);
         //For backwards compatibility. Must be after the changed notification (otherwise the compression removes it).
         if (changes.contains(AKONADI_PARAM_ENABLED)) {
diff --git a/src/server/handlerhelper.h b/src/server/handlerhelper.h
--- a/src/server/handlerhelper.h
+++ b/src/server/handlerhelper.h
@@ -90,7 +90,6 @@
             int ancestorDepth = 0,
             const QStack<Collection> &ancestors = QStack<Collection>(),
             const QStack<CollectionAttribute::List> &ancestorAttributes = QStack<CollectionAttribute::List>(),
-            bool isReferenced = false,
             const QStringList &mimeTypes = QStringList());
 
     /**
diff --git a/src/server/handlerhelper.cpp b/src/server/handlerhelper.cpp
--- a/src/server/handlerhelper.cpp
+++ b/src/server/handlerhelper.cpp
@@ -103,16 +103,15 @@
     }
 
     return fetchCollectionsResponse(col, col.attributes(), false, 0, QStack<Collection>(),
-                                    QStack<CollectionAttribute::List>(), false, mimeTypes);
+                                    QStack<CollectionAttribute::List>(), mimeTypes);
 }
 
 Protocol::FetchCollectionsResponse HandlerHelper::fetchCollectionsResponse(const Collection &col,
         const CollectionAttribute::List &attrs,
         bool includeStatistics,
         int ancestorDepth,
         const QStack<Collection> &ancestors,
         const QStack<CollectionAttribute::List> &ancestorAttributes,
-        bool isReferenced,
         const QStringList &mimeTypes)
 {
     Protocol::FetchCollectionsResponse response;
@@ -156,7 +155,6 @@
         response.setAncestors(ancestorList);
     }
 
-    response.setReferenced(isReferenced);
     response.setEnabled(col.enabled());
     response.setDisplayPref(static_cast<Tristate>(col.displayPref()));
     response.setSyncPref(static_cast<Tristate>(col.syncPref()));
diff --git a/src/server/notificationsubscriber.cpp b/src/server/notificationsubscriber.cpp
--- a/src/server/notificationsubscriber.cpp
+++ b/src/server/notificationsubscriber.cpp
@@ -20,7 +20,6 @@
 #include "notificationsubscriber.h"
 #include "akonadiserver_debug.h"
 #include "notificationmanager.h"
-#include "collectionreferencemanager.h"
 #include "aggregatedfetchscope.h"
 #include "utils.h"
 
@@ -398,22 +397,6 @@
         return false;
     }
 
-    if (CollectionReferenceManager::instance()->isReferenced(msg.parentCollection())) {
-        //We always want notifications that affect the parent resource (like an item added to a referenced collection)
-        const bool notificationForParentResource = (mSession == msg.resource());
-        const bool accepts = mExclusive
-                             || isCollectionMonitored(msg.parentCollection())
-                             || isMoveDestinationResourceMonitored(msg)
-                             || notificationForParentResource;
-        TRACE_NTF("ACCEPTS ITEM: parent col referenced"
-                  << "exclusive:" << mExclusive << ","
-                  << "parent monitored:" << isCollectionMonitored(msg.parentCollection()) << ","
-                  << "destination monitored:" << isMoveDestinationResourceMonitored(msg) << ","
-                  << "ntf for parent resource:" << notificationForParentResource << ":"
-                  << "ACCEPTED:" << accepts);
-        return accepts;
-    }
-
     if (mAllMonitored) {
         TRACE_NTF("ACCEPTS ITEM: all monitored");
         return true;
@@ -489,25 +472,8 @@
             return true;
         }
 
-        //Deliver the notification if referenced from this session
-        if (CollectionReferenceManager::instance()->isReferenced(collection.id(), mSession)) {
-            return true;
-        }
-
-        //Exclusive subscribers still want the notification
-        if (mExclusive && CollectionReferenceManager::instance()->isReferenced(collection.id())) {
-            return true;
-        }
-
-        //The session belonging to this monitor referenced or dereferenced the collection. We always want this notification.
-        //The referencemanager no longer holds a reference, so we have to check this way.
-        if (msg.changedParts().contains(AKONADI_PARAM_REFERENCED) && mSession == msg.sessionId()) {
-            return true;
-        }
-
-        // If the collection is not referenced, monitored or the subscriber is not
-        // exclusive (i.e. if we got here), then the subscriber does not care about
-        // this one, so drop it
+        // If the subscriber is not exclusive (i.e. if we got here), then the subscriber does
+        // not care about this one, so drop it
         return false;
     }
 
@@ -678,20 +644,6 @@
     }
 }
 
-Protocol::CollectionChangeNotificationPtr NotificationSubscriber::customizeCollection(const Protocol::CollectionChangeNotificationPtr &ntf)
-{
-    const bool isReferencedFromSession = CollectionReferenceManager::instance()->isReferenced(ntf->collection().id(), mSession);
-    if (isReferencedFromSession != ntf->collection().referenced()) {
-        auto copy = Protocol::CollectionChangeNotificationPtr::create(*ntf);
-        auto copyCol = ntf->collection();
-        copyCol.setReferenced(isReferencedFromSession);
-        copy->setCollection(std::move(copyCol));
-        return copy;
-    }
-
-    return ntf;
-}
-
 bool NotificationSubscriber::notify(const Protocol::ChangeNotificationPtr &notification)
 {
     // Guard against this object being deleted while we are waiting for the lock
@@ -702,12 +654,8 @@
     }
 
     if (acceptsNotification(*notification)) {
-        auto ntf = notification;
-        if (ntf->type() == Protocol::Command::CollectionChangeNotification) {
-            ntf = customizeCollection(notification.staticCast<Protocol::CollectionChangeNotification>());
-        }
         QMetaObject::invokeMethod(this, "writeNotification", Qt::QueuedConnection,
-                                  Q_ARG(Akonadi::Protocol::ChangeNotificationPtr, ntf));
+                                  Q_ARG(Akonadi::Protocol::ChangeNotificationPtr, notification));
         return true;
     }
     return false;
diff --git a/src/server/preprocessormanager.cpp b/src/server/preprocessormanager.cpp
--- a/src/server/preprocessormanager.cpp
+++ b/src/server/preprocessormanager.cpp
@@ -29,8 +29,6 @@
 #include "storage/datastore.h"
 #include "tracer.h"
 
-#include "collectionreferencemanager.h"
-
 #include "preprocessormanageradaptor.h"
 
 namespace Akonadi
@@ -230,8 +228,8 @@
     Q_ASSERT_X(item.hidden(), "PreprocessorManager::beginHandleItem()", "The item you pass to this function should be hidden!");
 #endif
 
-    if (mPreprocessorChain.isEmpty() || CollectionReferenceManager::instance()->isReferenced(item.collectionId())) {
-        // No preprocessors at all or referenced collection: immediately end handling the item.
+    if (mPreprocessorChain.isEmpty()) {
+        // No preprocessors at all: immediately end handling the item.
         lockedEndHandleItem(item.id());
         return;
     }
diff --git a/src/server/storage/akonadidb.xml b/src/server/storage/akonadidb.xml
--- a/src/server/storage/akonadidb.xml
+++ b/src/server/storage/akonadidb.xml
@@ -67,7 +67,7 @@
     <comment>Contains the schema version of the database.</comment>
     <column name="version" type="int" default="0" allowNull="false"/>
     <column name="generation" type="int" default="0" allowNull="false" />
-    <data columns="version" values="39"/>
+    <data columns="version" values="40"/>
   </table>
 
   <table name="Resource">
@@ -95,7 +95,6 @@
     <column name="syncPref" type="enum" enumType="Tristate" default="Tristate::Undefined"/>
     <column name="displayPref" type="enum" enumType="Tristate" default="Tristate::Undefined"/>
     <column name="indexPref" type="enum" enumType="Tristate" default="Tristate::Undefined"/>
-    <column name="referenced" type="bool" default="false" allowNull="false"/>
     <column name="cachePolicyInherit" type="bool" default="true" allowNull="false"/>
     <column name="cachePolicyCheckInterval" type="int" default="-1" allowNull="false"/>
     <column name="cachePolicyCacheTimeout" type="int" default="-1" allowNull="false"/>
diff --git a/src/server/storage/notificationcollector.cpp b/src/server/storage/notificationcollector.cpp
--- a/src/server/storage/notificationcollector.cpp
+++ b/src/server/storage/notificationcollector.cpp
@@ -155,7 +155,7 @@
     if (auto checker = AkonadiServer::instance()->intervalChecker()) {
         checker->collectionChanged(collection.id());
     }
-    if (changes.contains(AKONADI_PARAM_ENABLED) || changes.contains(AKONADI_PARAM_REFERENCED)) {
+    if (changes.contains(AKONADI_PARAM_ENABLED)) {
         CollectionStatistics::self()->invalidateCollection(collection);
     }
     collectionNotification(Protocol::CollectionChangeNotification::Modify, collection, collection.parentId(),
@@ -407,7 +407,7 @@
             for (const auto &mt : mts) {
                 mimeTypes.push_back(mt.name());
             }
-            msgCollection = HandlerHelper::fetchCollectionsResponse(col, {}, false, 0, {}, {}, false, mimeTypes);
+            msgCollection = HandlerHelper::fetchCollectionsResponse(col, {}, false, 0, {}, {}, mimeTypes);
         }
         // Get up-to-date statistics
         if (fetchScope->fetchStatistics()) {