diff --git a/messagelist/src/utils/aggregationcombobox.cpp b/messagelist/src/utils/aggregationcombobox.cpp
index 40ed7d2b..5577229c 100644
--- a/messagelist/src/utils/aggregationcombobox.cpp
+++ b/messagelist/src/utils/aggregationcombobox.cpp
@@ -1,141 +1,141 @@
 /* Copyright 2009 James Bendig <james@imptalk.com>
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of
    the License or (at your option) version 3 or any later version
    accepted by the membership of KDE e.V. (or its successor approved
    by the membership of KDE e.V.), which shall act as a proxy
    defined in Section 14 of version 3 of the license.
 
    This program 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 General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 #include "aggregationcombobox.h"
 #include "aggregationcombobox_p.h"
 
 #include "core/aggregation.h"
 #include "core/manager.h"
 #include "messagelistsettings.h"
 #include "storagemodel.h"
 
 using namespace MessageList::Core;
 using namespace MessageList::Utils;
 
 AggregationComboBox::AggregationComboBox(QWidget *parent)
-    : KComboBox(parent)
+    : QComboBox(parent)
     , d(new AggregationComboBoxPrivate(this))
 {
     if (Manager::instance()) {
         d->slotLoadAggregations();
     } else {
         setEnabled(false);
     }
 }
 
 AggregationComboBox::~AggregationComboBox()
 {
     delete d;
 }
 
 QString AggregationComboBox::currentAggregation() const
 {
     return itemData(currentIndex()).toString();
 }
 
 void AggregationComboBox::writeDefaultConfig() const
 {
     KConfigGroup group(MessageListSettings::self()->config(), "MessageListView::StorageModelAggregations");
 
     const QString aggregationID = currentAggregation();
     group.writeEntry(QStringLiteral("DefaultSet"), aggregationID);
 
     if (Manager::instance()) {
         Manager::instance()->aggregationsConfigurationCompleted();
     }
 }
 
 void AggregationComboBox::writeStorageModelConfig(MessageList::Core::StorageModel *storageModel, bool isPrivateSetting) const
 {
     writeStorageModelConfig(storageModel->id(), isPrivateSetting);
 }
 
 void AggregationComboBox::writeStorageModelConfig(const QString &id, bool isPrivateSetting) const
 {
     if (Manager::instance()) {
         // message list aggregation
         QString aggregationID;
         if (isPrivateSetting) {
             aggregationID = currentAggregation();
         } else { // explicitly use default aggregation id when using default aggregation.
             aggregationID = Manager::instance()->defaultAggregation()->id();
         }
         Manager::instance()->saveAggregationForStorageModel(id, aggregationID, isPrivateSetting);
         Manager::instance()->aggregationsConfigurationCompleted();
     }
 }
 
 void AggregationComboBox::readStorageModelConfig(const QString &id, bool &isPrivateSetting)
 {
     if (Manager::instance()) {
         const Aggregation *aggregation = Manager::instance()->aggregationForStorageModel(id, &isPrivateSetting);
         d->setCurrentAggregation(aggregation);
     }
 }
 
 void AggregationComboBox::readStorageModelConfig(MessageList::Core::StorageModel *storageModel, bool &isPrivateSetting)
 {
     readStorageModelConfig(storageModel->id(), isPrivateSetting);
 }
 
 void AggregationComboBox::readStorageModelConfig(const Akonadi::Collection &col, bool &isPrivateSetting)
 {
     if (col.isValid()) {
         readStorageModelConfig(QString::number(col.id()), isPrivateSetting);
     }
 }
 
 void AggregationComboBox::selectDefault()
 {
     if (Manager::instance()) {
         const Aggregation *defaultAggregation = Manager::instance()->defaultAggregation();
         d->setCurrentAggregation(defaultAggregation);
     }
 }
 
 void AggregationComboBox::slotLoadAggregations()
 {
     d->slotLoadAggregations();
 }
 
 void AggregationComboBoxPrivate::slotLoadAggregations()
 {
     if (!Manager::instance()) {
         return;
     }
     q->clear();
 
     // Get all message list aggregations and sort them into alphabetical order.
     QList< Aggregation * > aggregations = Manager::instance()->aggregations().values();
     std::sort(aggregations.begin(), aggregations.end(), MessageList::Core::Aggregation::compareName);
 
     for (const Aggregation *aggregation : qAsConst(aggregations)) {
         q->addItem(aggregation->name(), QVariant(aggregation->id()));
     }
 }
 
 void AggregationComboBoxPrivate::setCurrentAggregation(const Aggregation *aggregation)
 {
     Q_ASSERT(aggregation != nullptr);
 
     const QString aggregationID = aggregation->id();
     const int aggregationIndex = q->findData(QVariant(aggregationID));
     q->setCurrentIndex(aggregationIndex);
 }
 
 #include "moc_aggregationcombobox.cpp"
diff --git a/messagelist/src/utils/aggregationcombobox.h b/messagelist/src/utils/aggregationcombobox.h
index 72986a70..0748122b 100644
--- a/messagelist/src/utils/aggregationcombobox.h
+++ b/messagelist/src/utils/aggregationcombobox.h
@@ -1,65 +1,65 @@
 /* Copyright 2009 James Bendig <james@imptalk.com>
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of
    the License or (at your option) version 3 or any later version
    accepted by the membership of KDE e.V. (or its successor approved
    by the membership of KDE e.V.), which shall act as a proxy
    defined in Section 14 of version 3 of the license.
 
    This program 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 General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 #ifndef MESSAGELIST_UTILS_AGGREGATIONCOMBOBOX_H
 #define MESSAGELIST_UTILS_AGGREGATIONCOMBOBOX_H
 
 #include <messagelist_export.h>
-#include <KComboBox>
+#include <QComboBox>
 #include <collection.h>
 namespace MessageList {
 namespace Core {
 class Aggregation;
 class StorageModel;
 }
 
 namespace Utils {
 class AggregationComboBoxPrivate;
 /**
- * A specialized KComboBox that lists all message list aggregations.
+ * A specialized QComboBox that lists all message list aggregations.
  */
-class MESSAGELIST_EXPORT AggregationComboBox : public KComboBox
+class MESSAGELIST_EXPORT AggregationComboBox : public QComboBox
 {
     Q_OBJECT
 
 public:
     explicit AggregationComboBox(QWidget *parent);
     ~AggregationComboBox();
 
     QString currentAggregation() const;
 
     void writeDefaultConfig() const;
 
     void writeStorageModelConfig(MessageList::Core::StorageModel *storageModel, bool isPrivateSetting) const;
     void writeStorageModelConfig(const QString &id, bool isPrivateSetting) const;
 
     void readStorageModelConfig(MessageList::Core::StorageModel *storageModel, bool &isPrivateSetting);
     void readStorageModelConfig(const Akonadi::Collection &col, bool &isPrivateSetting);
     void readStorageModelConfig(const QString &id, bool &isPrivateSetting);
 
 public Q_SLOTS:
     void selectDefault();
     void slotLoadAggregations();
 
 private:
     AggregationComboBoxPrivate *const d;
 };
 } // namespace Utils
 } // namespace MessageList
 
 #endif //!__MESSAGELIST_UTILS_AGGREGATIONCOMBOBOX_H
diff --git a/messageviewer/src/ui/settings.ui b/messageviewer/src/ui/settings.ui
index 63dff324..ae42428d 100644
--- a/messageviewer/src/ui/settings.ui
+++ b/messageviewer/src/ui/settings.ui
@@ -1,261 +1,261 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <ui version="4.0">
  <author>/*  Copyright (C) 2009 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.net
   Copyright (c) 2009 Andras Mantia &lt;andras@kdab.net&gt;
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
 
   This program 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 General Public License for more details.
 
   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the Free Software Foundation, Inc.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */</author>
  <class>Settings</class>
  <widget class="QWidget" name="Settings">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>482</width>
     <height>456</height>
    </rect>
   </property>
   <property name="windowTitle">
    <string>Viewer settings</string>
   </property>
   <layout class="QGridLayout" name="gridLayout">
    <item row="1" column="0">
     <spacer name="verticalSpacer_2">
      <property name="orientation">
       <enum>Qt::Vertical</enum>
      </property>
      <property name="sizeType">
       <enum>QSizePolicy::Fixed</enum>
      </property>
      <property name="sizeHint" stdset="0">
       <size>
        <width>20</width>
        <height>24</height>
       </size>
      </property>
     </spacer>
    </item>
    <item row="2" column="0" colspan="2">
     <widget class="QLabel" name="label_3">
      <property name="sizePolicy">
       <sizepolicy hsizetype="Preferred" vsizetype="Maximum">
        <horstretch>0</horstretch>
        <verstretch>0</verstretch>
       </sizepolicy>
      </property>
      <property name="text">
       <string>O&amp;verride character encoding:</string>
      </property>
      <property name="buddy">
       <cstring>overrideCharacterEncoding</cstring>
      </property>
     </widget>
    </item>
    <item row="2" column="2">
-    <widget class="KComboBox" name="overrideCharacterEncoding">
+    <widget class="QComboBox" name="overrideCharacterEncoding">
      <property name="sizePolicy">
       <sizepolicy hsizetype="Preferred" vsizetype="Maximum">
        <horstretch>0</horstretch>
        <verstretch>0</verstretch>
       </sizepolicy>
      </property>
     </widget>
    </item>
    <item row="3" column="2">
     <widget class="QSpinBox" name="kcfg_MinimumFontSize">
      <property name="minimum">
       <number>2</number>
      </property>
      <property name="maximum">
       <number>30</number>
      </property>
     </widget>
    </item>
    <item row="0" column="0" colspan="3">
     <layout class="QVBoxLayout" name="verticalLayout">
      <item>
       <widget class="QCheckBox" name="kcfg_AccessKeyEnabled">
        <property name="text">
         <string>Enable access key</string>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QCheckBox" name="kcfg_ShrinkQuotes">
        <property name="text">
         <string>Reduce font size for &amp;quoted text</string>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QCheckBox" name="kcfg_ShowExpandQuotesMark">
        <property name="text">
         <string>Show &amp;expand/collapse quote marks</string>
        </property>
       </widget>
      </item>
      <item>
       <layout class="QHBoxLayout" name="horizontalLayout_2">
        <item>
         <spacer name="horizontalSpacer">
          <property name="orientation">
           <enum>Qt::Horizontal</enum>
          </property>
          <property name="sizeType">
           <enum>QSizePolicy::Fixed</enum>
          </property>
          <property name="sizeHint" stdset="0">
           <size>
            <width>24</width>
            <height>20</height>
           </size>
          </property>
         </spacer>
        </item>
        <item>
         <widget class="QLabel" name="collapseQuoteLevelLabel">
          <property name="enabled">
           <bool>false</bool>
          </property>
          <property name="text">
           <string>Automatic collapse &amp;level:</string>
          </property>
          <property name="buddy">
           <cstring>kcfg_CollapseQuoteLevelSpin</cstring>
          </property>
         </widget>
        </item>
        <item>
         <widget class="QSpinBox" name="kcfg_CollapseQuoteLevelSpin">
          <property name="enabled">
           <bool>false</bool>
          </property>
          <property name="minimum">
           <number>1</number>
          </property>
          <property name="maximum">
           <number>3</number>
          </property>
          <property name="value">
           <number>3</number>
          </property>
         </widget>
        </item>
        <item>
         <spacer name="horizontalSpacer_2">
          <property name="orientation">
           <enum>Qt::Horizontal</enum>
          </property>
          <property name="sizeHint" stdset="0">
           <size>
            <width>40</width>
            <height>20</height>
           </size>
          </property>
         </spacer>
        </item>
       </layout>
      </item>
     </layout>
    </item>
    <item row="3" column="3">
     <spacer name="horizontalSpacer_3">
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
      </property>
      <property name="sizeHint" stdset="0">
       <size>
        <width>40</width>
        <height>20</height>
       </size>
      </property>
     </spacer>
    </item>
    <item row="9" column="0" colspan="3">
     <spacer name="verticalSpacer">
      <property name="orientation">
       <enum>Qt::Vertical</enum>
      </property>
      <property name="sizeHint" stdset="0">
       <size>
        <width>20</width>
        <height>40</height>
       </size>
      </property>
     </spacer>
    </item>
    <item row="3" column="0">
     <widget class="QLabel" name="label_4">
      <property name="text">
       <string>&amp;Minimum font size:</string>
      </property>
      <property name="buddy">
       <cstring>kcfg_MinimumFontSize</cstring>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <customwidgets>
   <customwidget>
-   <class>KComboBox</class>
+   <class>QComboBox</class>
    <extends>QComboBox</extends>
    <header>kcombobox.h</header>
   </customwidget>
  </customwidgets>
  <tabstops>
   <tabstop>kcfg_AccessKeyEnabled</tabstop>
   <tabstop>kcfg_ShrinkQuotes</tabstop>
   <tabstop>kcfg_ShowExpandQuotesMark</tabstop>
   <tabstop>kcfg_CollapseQuoteLevelSpin</tabstop>
   <tabstop>overrideCharacterEncoding</tabstop>
   <tabstop>kcfg_MinimumFontSize</tabstop>
  </tabstops>
  <resources/>
  <connections>
   <connection>
    <sender>kcfg_ShowExpandQuotesMark</sender>
    <signal>toggled(bool)</signal>
    <receiver>collapseQuoteLevelLabel</receiver>
    <slot>setEnabled(bool)</slot>
    <hints>
     <hint type="sourcelabel">
      <x>94</x>
      <y>125</y>
     </hint>
     <hint type="destinationlabel">
      <x>138</x>
      <y>153</y>
     </hint>
    </hints>
   </connection>
   <connection>
    <sender>kcfg_ShowExpandQuotesMark</sender>
    <signal>toggled(bool)</signal>
    <receiver>kcfg_CollapseQuoteLevelSpin</receiver>
    <slot>setEnabled(bool)</slot>
    <hints>
     <hint type="sourcelabel">
      <x>179</x>
      <y>125</y>
     </hint>
     <hint type="destinationlabel">
      <x>228</x>
      <y>153</y>
     </hint>
    </hints>
   </connection>
  </connections>
 </ui>
diff --git a/messageviewer/src/widgets/configurewidget.cpp b/messageviewer/src/widgets/configurewidget.cpp
index 1ababa31..6394ffcb 100644
--- a/messageviewer/src/widgets/configurewidget.cpp
+++ b/messageviewer/src/widgets/configurewidget.cpp
@@ -1,122 +1,122 @@
 /*
   Copyright (C) 2009 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.net
   Copyright (c) 2009 Andras Mantia <andras@kdab.net>
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
 
   This program 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 General Public License for more details.
 
   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the Free Software Foundation, Inc.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
 
 #include "configurewidget.h"
 #include "messageviewer_debug.h"
 #include "ui_settings.h"
 #include "utils/messageviewerutil.h"
 #include "settings/messageviewersettings.h"
 #include <MimeTreeParser/NodeHelper>
 
 #include "MessageCore/MessageCoreSettings"
 
 #include <KLocalizedString>
 
 using namespace MessageViewer;
 
 class MessageViewer::ConfigureWidgetPrivate
 {
 public:
     ConfigureWidgetPrivate()
     {
     }
 
     ~ConfigureWidgetPrivate()
     {
         delete mSettingsUi;
         mSettingsUi = nullptr;
     }
 
     Ui_Settings *mSettingsUi = nullptr;
 };
 
 ConfigureWidget::ConfigureWidget(QWidget *parent)
     : QWidget(parent)
     , d(new MessageViewer::ConfigureWidgetPrivate)
 {
     d->mSettingsUi = new Ui_Settings;
     d->mSettingsUi->setupUi(this);
     layout()->setContentsMargins(0, 0, 0, 0);
 
     QStringList encodings = MimeTreeParser::NodeHelper::supportedEncodings(false);
     encodings.prepend(i18n("Auto"));
     d->mSettingsUi->overrideCharacterEncoding->addItems(encodings);
     d->mSettingsUi->overrideCharacterEncoding->setCurrentIndex(0);
 
     d->mSettingsUi->overrideCharacterEncoding->setWhatsThis(
         MessageCore::MessageCoreSettings::self()->overrideCharacterEncodingItem()->whatsThis());
     d->mSettingsUi->kcfg_ShrinkQuotes->setWhatsThis(
         MessageViewer::MessageViewerSettings::self()->shrinkQuotesItem()->whatsThis());
     d->mSettingsUi->kcfg_ShowExpandQuotesMark->setWhatsThis(
         MessageViewer::MessageViewerSettings::self()->showExpandQuotesMarkItem()->whatsThis());
 
-    connect(d->mSettingsUi->overrideCharacterEncoding, QOverload<int>::of(&KComboBox::currentIndexChanged), this,
+    connect(d->mSettingsUi->overrideCharacterEncoding, QOverload<int>::of(&QComboBox::currentIndexChanged), this,
             &ConfigureWidget::settingsChanged);
 }
 
 ConfigureWidget::~ConfigureWidget()
 {
     delete d;
 }
 
 void ConfigureWidget::readConfig()
 {
     readCurrentOverrideCodec();
     d->mSettingsUi->kcfg_CollapseQuoteLevelSpin->setEnabled(
         MessageViewer::MessageViewerSettings::self()->showExpandQuotesMark());
 }
 
 void ConfigureWidget::writeConfig()
 {
     MessageCore::MessageCoreSettings::self()->setOverrideCharacterEncoding(
         d->mSettingsUi->overrideCharacterEncoding->currentIndex() == 0
         ? QString()
         : MimeTreeParser::NodeHelper::encodingForName(d->mSettingsUi->overrideCharacterEncoding->
                                                       currentText()));
 }
 
 void ConfigureWidget::readCurrentOverrideCodec()
 {
     const QString &currentOverrideEncoding
         = MessageCore::MessageCoreSettings::self()->overrideCharacterEncoding();
     if (currentOverrideEncoding.isEmpty()) {
         d->mSettingsUi->overrideCharacterEncoding->setCurrentIndex(0);
         return;
     }
     QStringList encodings = MimeTreeParser::NodeHelper::supportedEncodings(false);
     encodings.prepend(i18n("Auto"));
     QStringList::ConstIterator it(encodings.constBegin());
     const QStringList::ConstIterator end(encodings.constEnd());
     int i = 0;
     for (; it != end; ++it) {
         if (MimeTreeParser::NodeHelper::encodingForName(*it) == currentOverrideEncoding) {
             d->mSettingsUi->overrideCharacterEncoding->setCurrentIndex(i);
             break;
         }
         ++i;
     }
     if (i == encodings.size()) {
         // the current value of overrideCharacterEncoding is an unknown encoding => reset to Auto
         qCWarning(MESSAGEVIEWER_LOG) << "Unknown override character encoding"
                                      << currentOverrideEncoding
                                      << ". Resetting to Auto.";
         d->mSettingsUi->overrideCharacterEncoding->setCurrentIndex(0);
         MessageCore::MessageCoreSettings::self()->setOverrideCharacterEncoding(QString());
     }
 }