Mark messages as modified

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

@@ -2214,6 +2214,7 @@ class Core {
                 : message.references + " " + message.msgid);
         MimeMessage icopy = new MimeMessageEx((MimeMessage) imessage, msgid);
         icopy.addHeader("References", MessageHelper.limitReferences(ref));
+        icopy.addHeader(MessageHelper.HEADER_MODIFIED_TIME, Long.toString(new Date().getTime()));
         MessageHelper helper = new MessageHelper(icopy, context);
         MessageHelper.MessageParts parts = helper.getMessageParts();
         List<MessageHelper.AttachmentPart> aparts = parts.getAttachmentParts();
@@ -3244,6 +3245,7 @@ class Core {
         MimeMessage icopy = new MimeMessageEx((MimeMessage) imessage, msgid);
         icopy.setSubject(subject); // Update or delete subject
         icopy.addHeader("References", MessageHelper.limitReferences(ref));
+        icopy.addHeader(MessageHelper.HEADER_MODIFIED_TIME, Long.toString(new Date().getTime()));
 
         ifolder.appendMessages(new Message[]{icopy});
 
@@ -4643,7 +4645,7 @@ class Core {
 
             Long received;
             long future = new Date().getTime() + FUTURE_RECEIVED;
-            if (account.use_date || EntityFolder.SENT.equals(folder.type)) {
+            if (account.use_date || EntityFolder.SENT.equals(folder.type) || helper.isModified()) {
                 received = sent;
                 if (received == null || received == 0 || received > future)
                     received = helper.getReceived();

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

@@ -180,6 +180,7 @@ public class MessageHelper {
     static final String HEADER_CORRELATION_ID = "X-Correlation-ID";
     static final String HEADER_MICROSOFT_ORIGINAL_MESSAGE_ID = "X-Microsoft-Original-Message-ID";
     static final String HEADER_GOOGLE_ORIGINAL_MESSAGE_ID = "X-Google-Original-Message-ID";
+    static final String HEADER_MODIFIED_TIME = "X-Modified-Time";
     static final int MAX_SUBJECT_AGE = 48; // hours
     static final int DEFAULT_THREAD_RANGE = 7; // 2^7 = 128 days
     static final int MAX_UNZIP_COUNT = 20;
@@ -3040,6 +3041,11 @@ public class MessageHelper {
         return (size < 0 ? null : size);
     }
 
+    boolean isModified() throws MessagingException {
+        ensureHeaders();
+        return (imessage.getHeader(HEADER_MODIFIED_TIME) != null);
+    }
+
     Long getReceived() throws MessagingException {
         ensureEnvelope();