Added option to turn on legacy receipt request headers

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

@@ -90,6 +90,7 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
     private SwitchCompat swRemoveSignatures;
     private SwitchCompat swReceipt;
     private Spinner spReceiptType;
+    private SwitchCompat swReceiptLegacy;
     private SwitchCompat swLookupMx;
 
     private final static String[] RESET_OPTIONS = new String[]{
@@ -102,7 +103,7 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
             "signature_location", "signature_new", "signature_reply", "signature_forward",
             "discard_delete", "reply_move",
             "auto_link", "plain_only", "format_flowed", "usenet_signature", "remove_signatures",
-            "receipt_default", "receipt_type", "lookup_mx"
+            "receipt_default", "receipt_type", "receipt_legacy", "lookup_mx"
     };
 
     @Override
@@ -154,6 +155,7 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
         swRemoveSignatures = view.findViewById(R.id.swRemoveSignatures);
         swReceipt = view.findViewById(R.id.swReceipt);
         spReceiptType = view.findViewById(R.id.spReceiptType);
+        swReceiptLegacy = view.findViewById(R.id.swReceiptLegacy);
         swLookupMx = view.findViewById(R.id.swLookupMx);
 
         String[] fontNameNames = getResources().getStringArray(R.array.fontNameNames);
@@ -474,6 +476,13 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
             }
         });
 
+        swReceiptLegacy.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("receipt_legacy", checked).apply();
+            }
+        });
+
         swLookupMx.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
@@ -598,6 +607,8 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
         int receipt_type = prefs.getInt("receipt_type", 2);
         spReceiptType.setSelection(receipt_type);
 
+        swReceiptLegacy.setChecked(prefs.getBoolean("receipt_legacy", false));
+
         swLookupMx.setChecked(prefs.getBoolean("lookup_mx", false));
     }
 }

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

@@ -253,6 +253,7 @@ public class MessageHelper {
         DB db = DB.getInstance(context);
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
         int receipt_type = prefs.getInt("receipt_type", 2);
+        boolean receipt_legacy = prefs.getBoolean("receipt_legacy", false);
         boolean hide_timezone = prefs.getBoolean("hide_timezone", true);
         boolean autocrypt = prefs.getBoolean("autocrypt", true);
         boolean mutual = prefs.getBoolean("autocrypt_mutual", true);
@@ -449,9 +450,11 @@ public class MessageHelper {
                 // 2=Read+delivery receipt
 
                 // defacto standard
-                if (receipt_type == 1 || receipt_type == 2) // Delivery receipt
+                if (receipt_type == 1 || receipt_type == 2) {
+                    // Delivery receipt
+                    if (receipt_legacy)
                         imessage.addHeader("Return-Receipt-To", to);
-
+                }
 
                 // https://tools.ietf.org/html/rfc3798
                 if (receipt_type == 0 || receipt_type == 2) {

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

@@ -738,6 +738,17 @@
                     app:layout_constraintStart_toStartOf="parent"
                     app:layout_constraintTop_toBottomOf="@id/tvReceiptType" />
 
+                <androidx.appcompat.widget.SwitchCompat
+                    android:id="@+id/swReceiptLegacy"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginTop="12dp"
+                    android:text="@string/title_identity_receipt_legacy"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@id/spReceiptType"
+                    app:switchPadding="12dp" />
+
                 <androidx.appcompat.widget.SwitchCompat
                     android:id="@+id/swLookupMx"
                     android:layout_width="0dp"
@@ -746,7 +757,7 @@
                     android:text="@string/title_advanced_lookup_mx"
                     app:layout_constraintEnd_toEndOf="parent"
                     app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toBottomOf="@id/spReceiptType"
+                    app:layout_constraintTop_toBottomOf="@id/swReceiptLegacy"
                     app:switchPadding="12dp" />
 
                 <eu.faircode.email.FixedTextView

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

@@ -839,6 +839,7 @@
     <string name="title_identity_unicode_remark">Most servers do not support this</string>
     <string name="title_identity_max_size">Maximum message size (MB)</string>
     <string name="title_identity_receipt">Request delivery/read receipt by default</string>
+    <string name="title_identity_receipt_legacy">Use legacy receipt request headers</string>
     <string name="title_identity_use_ip_hint">In case of \'invalid greeting\', \'requires valid address\' or a similar error, try to change this setting</string>
     <string name="title_identity_self_hint">Also prevents you from replying to yourself</string>
     <string name="title_optional">Optional</string>