diff --git a/app/src/main/java/eu/faircode/email/FragmentMessages.java b/app/src/main/java/eu/faircode/email/FragmentMessages.java
index 8a9abcd25a..cede5be5bc 100644
--- a/app/src/main/java/eu/faircode/email/FragmentMessages.java
+++ b/app/src/main/java/eu/faircode/email/FragmentMessages.java
@@ -5352,17 +5352,33 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
             return true;
         }
 
+        final Context context = getContext();
+        if (context == null)
+            return true;
+
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        boolean expand_first = prefs.getBoolean("expand_first", true);
+        boolean expand_all = prefs.getBoolean("expand_all", false);
+        long download = prefs.getInt("download", MessageHelper.DEFAULT_DOWNLOAD_SIZE);
+        boolean dup_msgids = prefs.getBoolean("dup_msgids", false);
+
         // Mark duplicates
         Map<String, List<TupleMessageEx>> duplicates = new HashMap<>();
-        for (TupleMessageEx message : messages)
-            if (message != null &&
-                    !TextUtils.isEmpty(message.hash)) {
-                if (!duplicates.containsKey(message.hash))
-                    duplicates.put(message.hash, new ArrayList<>());
-                duplicates.get(message.hash).add(message);
-            }
-        for (String hash : duplicates.keySet()) {
-            List<TupleMessageEx> dups = duplicates.get(hash);
+        for (TupleMessageEx message : messages) {
+            if (message == null)
+                continue;
+
+            String key = (dup_msgids ? message.msgid : message.hash);
+            if (TextUtils.isEmpty(key))
+                continue;
+
+            if (!duplicates.containsKey(key))
+                duplicates.put(key, new ArrayList<>());
+            duplicates.get(key).add(message);
+        }
+
+        for (String key : duplicates.keySet()) {
+            List<TupleMessageEx> dups = duplicates.get(key);
             int base = 0;
             for (int i = 0; i < dups.size(); i++)
                 if (dups.get(i).folder == folder) {
@@ -5376,16 +5392,10 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
 
         if (autoExpanded) {
             autoExpanded = false;
-
-            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getContext());
-            boolean expand_first = prefs.getBoolean("expand_first", true);
-            boolean expand_all = prefs.getBoolean("expand_all", false);
-            long download = prefs.getInt("download", MessageHelper.DEFAULT_DOWNLOAD_SIZE);
-
             if (download == 0)
                 download = Long.MAX_VALUE;
 
-            boolean unmetered = ConnectionHelper.getNetworkState(getContext()).isUnmetered();
+            boolean unmetered = ConnectionHelper.getNetworkState(context).isUnmetered();
 
             int count = 0;
             int unseen = 0;
diff --git a/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java b/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java
index b08311302c..d4d923df6b 100644
--- a/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java
+++ b/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java
@@ -141,6 +141,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
     private SwitchCompat swAuthNtlm;
     private SwitchCompat swAuthSasl;
     private SwitchCompat swExactAlarms;
+    private SwitchCompat swDupMsgId;
     private SwitchCompat swTestIab;
     private TextView tvProcessors;
     private TextView tvMemoryClass;
@@ -170,7 +171,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
             "protocol", "debug", "log_level",
             "use_modseq", "perform_expunge",
             "auth_plain", "auth_login", "auth_ntlm", "auth_sasl",
-            "exact_alarms", "test_iab"
+            "exact_alarms", "dup_msgids", "test_iab"
     };
 
     private final static String[] RESET_QUESTIONS = new String[]{
@@ -263,6 +264,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
         swAuthNtlm = view.findViewById(R.id.swAuthNtlm);
         swAuthSasl = view.findViewById(R.id.swAuthSasl);
         swExactAlarms = view.findViewById(R.id.swExactAlarms);
+        swDupMsgId = view.findViewById(R.id.swDupMsgId);
         swTestIab = view.findViewById(R.id.swTestIab);
         tvProcessors = view.findViewById(R.id.tvProcessors);
         tvMemoryClass = view.findViewById(R.id.tvMemoryClass);
@@ -742,6 +744,13 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
             }
         });
 
+        swDupMsgId.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("dup_msgids", checked).apply();
+            }
+        });
+
         swTestIab.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
@@ -1223,6 +1232,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
         swAuthNtlm.setChecked(prefs.getBoolean("auth_ntlm", true));
         swAuthSasl.setChecked(prefs.getBoolean("auth_sasl", true));
         swExactAlarms.setChecked(prefs.getBoolean("exact_alarms", true));
+        swDupMsgId.setChecked(prefs.getBoolean("dup_msgids", false));
         swTestIab.setChecked(prefs.getBoolean("test_iab", false));
 
         tvProcessors.setText(getString(R.string.title_advanced_processors, Runtime.getRuntime().availableProcessors()));
diff --git a/app/src/main/res/layout/fragment_options_misc.xml b/app/src/main/res/layout/fragment_options_misc.xml
index 899d44ddee..99f377b2a1 100644
--- a/app/src/main/res/layout/fragment_options_misc.xml
+++ b/app/src/main/res/layout/fragment_options_misc.xml
@@ -815,6 +815,17 @@
                     app:layout_constraintTop_toBottomOf="@id/swAuthSasl"
                     app:switchPadding="12dp" />
 
+                <androidx.appcompat.widget.SwitchCompat
+                    android:id="@+id/swDupMsgId"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginTop="12dp"
+                    android:text="@string/title_advanced_dup_msgid"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@id/swExactAlarms"
+                    app:switchPadding="12dp" />
+
                 <androidx.appcompat.widget.SwitchCompat
                     android:id="@+id/swTestIab"
                     android:layout_width="0dp"
@@ -823,7 +834,7 @@
                     android:text="@string/title_advanced_test_iab"
                     app:layout_constraintEnd_toEndOf="parent"
                     app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toBottomOf="@id/swExactAlarms"
+                    app:layout_constraintTop_toBottomOf="@id/swDupMsgId"
                     app:switchPadding="12dp" />
 
                 <eu.faircode.email.FixedTextView
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 594efb3b9d..c95427f26d 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -658,6 +658,7 @@
     <string name="title_advanced_auth_ntlm" translatable="false">NTLM</string>
     <string name="title_advanced_auth_sasl" translatable="false">SASL</string>
     <string name="title_advanced_exact_alarms" translatable="false">Use exact timers</string>
+    <string name="title_advanced_dup_msgid" translatable="false">Duplicates by message ID</string>
     <string name="title_advanced_test_iab" translatable="false">Test IAB</string>
     <string name="title_advanced_processors" translatable="false">Processors: %1$d</string>
     <string name="title_advanced_memory_class" translatable="false">Memory class: %1$s/%2$s Total: %3$s</string>