For my own convenience

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

@@ -1494,6 +1494,25 @@ public class MessageHelper {
                 }
         }
 
+        if (thread == null && BuildConfig.DEBUG) {
+            String awsses = imessage.getHeader("X-SES-Outgoing", null);
+            if (!TextUtils.isEmpty(awsses)) {
+                Address[] froms = getFrom();
+                if (froms != null && froms.length > 0) {
+                    String from = ((InternetAddress) froms[0]).getAddress();
+                    if (!TextUtils.isEmpty(from) && from.endsWith("@faircode.eu")) {
+                        Address[] rr = getReply();
+                        Address[] tos = (rr != null && rr.length > 0 ? rr : getTo());
+                        if (tos != null && tos.length > 0) {
+                            String email = ((InternetAddress) tos[0]).getAddress();
+                            if (!TextUtils.isEmpty(email))
+                                thread = "ses:" + email;
+                        }
+                    }
+                }
+            }
+        }
+
         // Common reference
         if (thread == null && refs.size() > 0) {
             String ref = refs.get(0);