(concat "+" (expand-file-name "spool" (elmo-folder-msgdb-path
                                             (, folder)))))))
 
-(defun elmo-dop-spool-folder-append-buffer (folder)
+(defun elmo-dop-spool-folder-append-buffer (folder flags)
   "Append current buffer content to the dop spool folder.
 FOLDER is the folder structure.
 Return a message number."
-  (setq folder (elmo-dop-spool-folder folder))
-  (unless (elmo-folder-exists-p folder)
-    (elmo-folder-create folder))
-  (let ((new-number (1+ (car (elmo-folder-status folder)))))
-    ;; dop folder is a localdir folder.
-    (write-region-as-binary (point-min) (point-max)
-                         (expand-file-name
-                          (int-to-string new-number)
-                          (elmo-localdir-folder-directory-internal folder))
-                         nil 'no-msg)
-    new-number))
+  (let ((spool (elmo-dop-spool-folder folder)))
+    (unless (elmo-folder-exists-p spool)
+      (elmo-folder-create spool))
+    (let ((new-number (1+ (car (elmo-folder-status spool)))))
+      (elmo-folder-append-buffer spool flags new-number)
+      new-number)))
 
 
 (defun elmo-dop-spool-folder-list-messages (folder)
                                 'car
                                 (car (elmo-dop-queue-arguments queue)))))))))
 
+(defun elmo-dop-filter-pending-messages (numbers)
+  (elmo-delete-if (lambda (number) (< number 0)) numbers))
+
 ;;; DOP operations.
 (defsubst elmo-folder-append-buffer-dop (folder &optional flag number)
   (elmo-dop-queue-append
    folder 'elmo-folder-append-buffer-dop-delayed
    (list flag
-        (elmo-dop-spool-folder-append-buffer
-         folder)
+        (elmo-dop-spool-folder-append-buffer folder flag)
         number)))
 
 (defsubst elmo-folder-delete-messages-dop (folder numbers)
   (elmo-dop-queue-append folder 'elmo-folder-create-dop-delayed nil))
 
 (defsubst elmo-folder-set-flag-dop (folder numbers flag)
-  (let ((method (case flag
-                 (unread
-                  'elmo-folder-unset-read-delayed)
-                 (read
-                  'elmo-folder-set-read-delayed)
-                 (important
-                  'elmo-folder-set-important-delayed)
-                 (answered
-                  'elmo-folder-set-answered-delayed))))
-    (if method
-       (elmo-dop-queue-append folder method (list numbers))
-      (elmo-dop-queue-append folder 'elmo-folder-set-flag
-                            (list numbers flag)))))
+  (when (setq numbers (elmo-dop-filter-pending-messages numbers))
+    (let ((method (case flag
+                   (unread
+                    'elmo-folder-unset-read-delayed)
+                   (read
+                    'elmo-folder-set-read-delayed)
+                   (important
+                    'elmo-folder-set-important-delayed)
+                   (answered
+                    'elmo-folder-set-answered-delayed))))
+      (if method
+         (elmo-dop-queue-append folder method (list numbers))
+       (elmo-dop-queue-append folder 'elmo-folder-set-flag
+                              (list numbers flag))))))
 
 (defsubst elmo-folder-unset-flag-dop (folder numbers flag)
-  (let ((method (case flag
-                 (unread
-                  'elmo-folder-set-read-delayed)
-                 (read
-                  'elmo-folder-unset-read-delayed)
-                 (important
-                  'elmo-folder-unset-important-delayed)
-                 (answered
-                  'elmo-folder-unset-answered-delayed))))
-    (if method
-       (elmo-dop-queue-append folder method (list numbers))
-      (elmo-dop-queue-append folder 'elmo-folder-unset-flag
-                            (list numbers flag)))))
+  (when (setq numbers (elmo-dop-filter-pending-messages numbers))
+    (let ((method (case flag
+                   (unread
+                    'elmo-folder-set-read-delayed)
+                   (read
+                    'elmo-folder-unset-read-delayed)
+                   (important
+                    'elmo-folder-unset-important-delayed)
+                   (answered
+                    'elmo-folder-unset-answered-delayed))))
+      (if method
+         (elmo-dop-queue-append folder method (list numbers))
+       (elmo-dop-queue-append folder 'elmo-folder-unset-flag
+                              (list numbers flag))))))
 
 ;;; Execute as subsutitute for plugged operation.
 (defun elmo-folder-status-dop (folder)
 ;;; Delayed operation (executed at online status).
 (defun elmo-folder-append-buffer-dop-delayed (folder flag number set-number)
   (let ((spool-folder (elmo-dop-spool-folder folder))
-       (flags (cond ((listp flag)
-                     flag)
-                    ;; for compatibility
-                    ((eq flag t)
-                     nil)
-                    (t
-                     (list flag))))
-       failure saved dequeued)
+       flags)
     (with-temp-buffer
-      (if (elmo-message-fetch spool-folder number
-                             (elmo-make-fetch-strategy 'entire)
-                             nil (current-buffer) 'unread)
-         (condition-case nil
-             (setq failure (not
-                            (elmo-folder-append-buffer
-                             folder
-                             flags
-                             set-number)))
-           (error (setq failure t)))
-       (setq dequeued t)) ; Already deletef from queue.
-      (when failure
-       ;; Append failed...
-       (setq saved (elmo-folder-append-buffer
-                    (elmo-make-folder elmo-lost+found-folder)
-                    flags
-                    set-number)))
-      (if (and (not dequeued)    ; if dequeued, no need to delete.
-              (or (not failure) ; succeed
-                  saved))       ; in lost+found
-         (elmo-folder-delete-messages spool-folder (list number)))
-      t)))
+      (when (elmo-message-fetch spool-folder number
+                               (elmo-make-fetch-strategy 'entire)
+                               nil (current-buffer) 'unread)
+       (setq flags (or (elmo-message-flags-for-append folder (* -1 number))
+                       (cond ((listp flag)
+                              flag)
+                             ;; for compatibility with 2.11.12 or earlier
+                             ((eq flag t)
+                              nil)
+                             (t
+                              (list flag)))))
+       (when (or (condition-case nil
+                     (elmo-folder-append-buffer folder flags set-number)
+                   (error))
+                 ;; Append failed...
+                 (elmo-folder-append-buffer
+                  (elmo-make-folder elmo-lost+found-folder)
+                  flags))
+         (elmo-folder-delete-messages spool-folder (list number)))))
+    ;; ignore failure (already dequed)
+    t))
 
 (defun elmo-folder-delete-messages-dop-delayed (folder number-alist)
   (ignore-errors
 
 FOLDER is a ELMO folder structure.
 NUMBER is a number of the message.")
 
+(defun elmo-message-flags-for-append (folder number &optional message-id)
+  "Return a list of flags for `elmo-folder-append-buffer'.
+FOLDER is a ELMO folder structure.
+NUMBER is a number of the message.
+If optional argument MESSAGES-ID is not specified, get it from current buffer."
+  (let ((this-id (elmo-message-field folder number 'message-id)))
+    (and this-id
+        (string= this-id (or message-id
+                             (elmo-msgdb-get-message-id-from-buffer)))
+        (or (elmo-message-flags folder number)
+            ;; message exists, but no flag.
+            '(read)))))
+
 (luna-define-method elmo-message-flag-available-p ((folder elmo-folder) number
                                                   flag)
   (elmo-msgdb-flag-available-p (elmo-folder-msgdb folder) flag))
                    (> (buffer-size) 0)
                    (elmo-folder-append-buffer
                     folder
-                    (let ((this-id (elmo-message-field src-folder (car numbers)
-                                                       'message-id)))
-                      (and this-id
-                           (string= this-id
-                                    (elmo-msgdb-get-message-id-from-buffer))
-                           (or (elmo-message-flags src-folder (car numbers))
-                               '(read))))
+                    (elmo-message-flags-for-append src-folder (car numbers))
                     (if same-number (car numbers))))))
          (error (setq failure t)))
        ;; FETCH & APPEND finished