Fixed reappearing POP3 messages

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

@@ -3136,8 +3136,7 @@ class Core {
                         for (int i = imessages.length - max; i < imessages.length; i++) {
                             Message imessage = imessages[i];
                             MessageHelper helper = new MessageHelper((MimeMessage) imessage, context);
-                            String msgid = helper.getMessageID(); // expensive!
+                            String msgid = helper.getPOP3MessageID(); // expensive!
-                            if (!TextUtils.isEmpty(msgid))
                             known.remove(msgid);
                         }
 
@@ -3175,15 +3174,7 @@ class Core {
                             }
                         } else {
                             uidl = null;
-                            msgid = helper.getMessageID();
+                            msgid = helper.getPOP3MessageID();
-
-                            if (TextUtils.isEmpty(msgid)) {
-                                Long time = helper.getSent();
-                                if (time == null)
-                                    msgid = helper.getHash();
-                                else
-                                    msgid = Long.toString(time);
-                            }
                         }
 
                         if (TextUtils.isEmpty(msgid)) {

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

@@ -1277,6 +1277,19 @@ public class MessageHelper {
         return (header == null ? null : MimeUtility.unfold(header));
     }
 
+    @NonNull
+    String getPOP3MessageID() throws MessagingException {
+        String msgid = getMessageID();
+        if (TextUtils.isEmpty(msgid)) {
+            Long time = getSent();
+            if (time == null)
+                msgid = getHash();
+            else
+                msgid = Long.toString(time);
+        }
+        return msgid;
+    }
+
     List<Header> getAllHeaders() throws MessagingException {
         ensureHeaders();
         return Collections.list(imessage.getAllHeaders());