From 1f1a2ac86ef3586e05ee7f1ba28ccc70f7260d45 Mon Sep 17 00:00:00 2001
From: M66B <M66B@users.noreply.github.com>
Date: Fri, 8 Sep 2023 18:34:06 +0200
Subject: [PATCH] Interpret Return-Receipt-To as read receipt request

---
 app/src/main/java/eu/faircode/email/MessageHelper.java | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/app/src/main/java/eu/faircode/email/MessageHelper.java b/app/src/main/java/eu/faircode/email/MessageHelper.java
index df71962155..c24de0822d 100644
--- a/app/src/main/java/eu/faircode/email/MessageHelper.java
+++ b/app/src/main/java/eu/faircode/email/MessageHelper.java
@@ -545,6 +545,7 @@ public class MessageHelper {
                 }
 
                 // https://tools.ietf.org/html/rfc3798
+                // https://en.wikipedia.org/wiki/Return_receipt
                 if (receipt_type == 0 || receipt_type == 2) {
                     // Read receipt
                     imessage.addHeader("Disposition-Notification-To", to);
@@ -2094,6 +2095,8 @@ public class MessageHelper {
         Address[] receipt = getAddressHeader("Disposition-Notification-To");
         if (receipt == null || receipt.length == 0)
             receipt = getAddressHeader("Read-Receipt-To");
+        if (receipt == null || receipt.length == 0)
+            receipt = getAddressHeader("Return-Receipt-To");
         if (receipt == null || receipt.length == 0)
             receipt = getAddressHeader("X-Confirm-Reading-To");
         return receipt;