Experiment: Outlook Thread-Index

app/src/main/java/eu/faircode/email/Core.java

@@ -3758,6 +3758,8 @@ class Core {
             // Local address contains control or whitespace in string ``mailing list someone@example.org''
             message.deliveredto = helper.getDeliveredTo();
             message.thread = helper.getThreadId(context, account.id, folder.id, uid);
+            if (BuildConfig.DEBUG && message.thread.startsWith("outlook:"))
+                message.warning = message.thread;
             message.priority = helper.getPriority();
 
             for (String keyword : keywords)

app/src/main/java/eu/faircode/email/FragmentOptionsSynchronize.java

@@ -81,6 +81,7 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
     private SwitchCompat swDeleteUnseen;
     private SwitchCompat swSyncKept;
     private SwitchCompat swGmailThread;
+    private SwitchCompat swOutlookThread;
     private SwitchCompat swSubjectThreading;
     private TextView tvSubjectThreading;
     private SwitchCompat swSyncFolders;
@@ -107,7 +108,7 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
             "enabled", "poll_interval", "auto_optimize", "schedule", "schedule_start", "schedule_end",
             "sync_quick_imap", "sync_quick_pop",
             "sync_nodate", "sync_unseen", "sync_flagged", "delete_unseen", "sync_kept",
-            "gmail_thread_id", "subject_threading",
+            "gmail_thread_id", "outlook_thread_id", "subject_threading",
             "sync_folders", "sync_folders_poll", "sync_shared_folders", "subscriptions",
             "check_authentication", "check_tls", "check_reply_domain", "check_mx", "check_blocklist", "use_blocklist",
             "tune_keep_alive"
@@ -153,6 +154,7 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
         swDeleteUnseen = view.findViewById(R.id.swDeleteUnseen);
         swSyncKept = view.findViewById(R.id.swSyncKept);
         swGmailThread = view.findViewById(R.id.swGmailThread);
+        swOutlookThread = view.findViewById(R.id.swOutlookThread);
         swSubjectThreading = view.findViewById(R.id.swSubjectThreading);
         tvSubjectThreading = view.findViewById(R.id.tvSubjectThreading);
         swSyncFolders = view.findViewById(R.id.swSyncFolders);
@@ -333,7 +335,15 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
                 prefs.edit().putBoolean("gmail_thread_id", checked).apply();
-                swSubjectThreading.setEnabled(!checked);
+                swSubjectThreading.setEnabled(!swGmailThread.isChecked() && !swOutlookThread.isChecked());
+            }
+        });
+
+        swOutlookThread.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("outlook_thread_id", checked).apply();
+                swSubjectThreading.setEnabled(!swGmailThread.isChecked() && !swOutlookThread.isChecked());
             }
         });
 
@@ -442,6 +452,7 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
         // Initialize
         FragmentDialogTheme.setBackground(getContext(), view, false);
 
+        swOutlookThread.setVisibility(BuildConfig.DEBUG ? View.VISIBLE : View.GONE);
         tvSubjectThreading.setText(getString(R.string.title_advanced_subject_threading_hint, MessageHelper.MAX_SUBJECT_AGE));
 
         DB db = DB.getInstance(getContext());
@@ -526,8 +537,9 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
         swDeleteUnseen.setChecked(prefs.getBoolean("delete_unseen", false));
         swSyncKept.setChecked(prefs.getBoolean("sync_kept", true));
         swGmailThread.setChecked(prefs.getBoolean("gmail_thread_id", false));
+        swOutlookThread.setChecked(prefs.getBoolean("outlook_thread_id", false));
         swSubjectThreading.setChecked(prefs.getBoolean("subject_threading", false));
-        swSubjectThreading.setEnabled(!swGmailThread.isChecked());
+        swSubjectThreading.setEnabled(!swGmailThread.isChecked() && !swOutlookThread.isChecked());
         swSyncFolders.setChecked(prefs.getBoolean("sync_folders", true));
         swSyncFoldersPoll.setChecked(prefs.getBoolean("sync_folders_poll", false));
         swSyncFoldersPoll.setEnabled(swSyncFolders.isChecked());

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -26,6 +26,7 @@ import android.content.SharedPreferences;
 import android.net.Uri;
 import android.system.ErrnoException;
 import android.text.TextUtils;
+import android.util.Base64;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -86,6 +87,7 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Properties;
 import java.util.TimeZone;
+import java.util.UUID;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -1390,11 +1392,35 @@ public class MessageHelper {
             boolean gmail_thread_id = prefs.getBoolean("gmail_thread_id", false);
             if (gmail_thread_id) {
                 long thrid = ((GmailMessage) imessage).getThrId();
+                Log.i("Gmail thread=" + thrid);
                 if (thrid > 0)
                     return "gmail:" + thrid;
             }
         }
 
+        // https://docs.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxomsg/9e994fbb-b839-495f-84e3-2c8c02c7dd9b
+        String tindex = imessage.getHeader("Thread-Index", null);
+        try {
+            if (tindex != null) {
+                boolean outlook_thread_id = prefs.getBoolean("outlook_thread_id", false);
+                if (outlook_thread_id) {
+                    byte[] data = Base64.decode(tindex, Base64.DEFAULT);
+                    if (data.length >= 22) {
+                        long msb = 0, lsb = 0;
+                        for (int i = 0 + 6; i < 8 + 6; i++)
+                            msb = (msb << 8) | (data[i] & 0xff);
+                        for (int i = 8 + 6; i < 16 + 6; i++)
+                            lsb = (lsb << 8) | (data[i] & 0xff);
+                        UUID guid = new UUID(msb, lsb);
+                        Log.i("Outlook thread=" + guid);
+                        return "outlook:" + guid;
+                    }
+                }
+            }
+        } catch (Throwable ex) {
+            Log.w(ex);
+        }
+
         String thread = null;
         String msgid = getMessageID();
 

app/src/main/res/layout/fragment_options_synchronize.xml

@@ -577,6 +577,29 @@
                     app:layout_constraintStart_toStartOf="parent"
                     app:layout_constraintTop_toBottomOf="@id/swGmailThread" />
 
+                <androidx.appcompat.widget.SwitchCompat
+                    android:id="@+id/swOutlookThread"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginTop="12dp"
+                    android:text="@string/title_advanced_outlook_thread"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@id/tvGmailThreadHint"
+                    app:switchPadding="12dp" />
+
+                <eu.faircode.email.FixedTextView
+                    android:id="@+id/tvOutlookThreadHint"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginEnd="48dp"
+                    android:text="@string/title_advanced_gmail_thread_hint"
+                    android:textAppearance="@style/TextAppearance.AppCompat.Small"
+                    android:textStyle="italic"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@id/swOutlookThread" />
+
                 <androidx.appcompat.widget.SwitchCompat
                     android:id="@+id/swSubjectThreading"
                     android:layout_width="0dp"
@@ -586,7 +609,7 @@
                     android:text="@string/title_advanced_subject_threading"
                     app:layout_constraintEnd_toEndOf="parent"
                     app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toBottomOf="@id/tvGmailThreadHint"
+                    app:layout_constraintTop_toBottomOf="@id/tvOutlookThreadHint"
                     app:switchPadding="12dp" />
 
                 <eu.faircode.email.FixedTextView

app/src/main/res/values/strings.xml

@@ -351,6 +351,7 @@
     <string name="title_advanced_delete_unseen">Delete old unread messages</string>
     <string name="title_advanced_kept_removed">Check if old messages were removed from the server</string>
     <string name="title_advanced_gmail_thread">Gmail message grouping style for Gmail accounts</string>
+    <string name="title_advanced_outlook_thread" translatable="false">Use Outlook thread index</string>
     <string name="title_advanced_subject_threading">Group messages by sender and subject</string>
     <string name="title_advanced_sync_folders">Synchronize folder list</string>
     <string name="title_advanced_sync_folders_poll">Actively synchronize folder list</string>