diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -79,7 +79,7 @@
 set(AKONADICALENDAR_LIB_VERSION "5.6.40")
 set(KONTACTINTERFACE_LIB_VERSION "5.6.40")
 set(AKONADIKALARM_LIB_VERSION "5.6.40")
-set(KMIME_LIB_VERSION "5.6.40")
+set(KMIME_LIB_VERSION "5.6.42")
 set(XMLRPCCLIENT_LIB_VERSION "5.6.40")
 set(KCONTACTS_LIB_VERSION "5.6.40")
 set(AKONADIMIME_LIB_VERSION "5.6.40")
diff --git a/plugins/akonadi_serializer_mail.cpp b/plugins/akonadi_serializer_mail.cpp
--- a/plugins/akonadi_serializer_mail.cpp
+++ b/plugins/akonadi_serializer_mail.cpp
@@ -191,12 +191,18 @@
             msg->date()->setDateTime(dt);
             stream >> str;
             msg->subject()->fromUnicodeString(str, QByteArrayLiteral("UTF-8"));
-            stream >> str;
-            msg->inReplyTo()->fromUnicodeString(str, QByteArrayLiteral("UTF-8"));
+
+            QString inReplyTo;
+            stream >> inReplyTo;
+            msg->inReplyTo()->fromUnicodeString(inReplyTo, QByteArrayLiteral("UTF-8"));
             stream >> str;
             msg->messageID()->fromUnicodeString(str, QByteArrayLiteral("UTF-8"));
             stream >> str;
-            msg->references()->fromUnicodeString(str, QByteArrayLiteral("UTF-8"));
+            if (str == inReplyTo) {
+                msg->references()->fromIdent(msg->inReplyTo());
+            } else {
+                msg->references()->fromUnicodeString(str, QByteArrayLiteral("UTF-8"));
+            }
 
             parseAddrList(stream, msg->from(), version, m_stringPool);
             parseAddrList(stream, msg->sender(), version, m_stringPool);