Can’t open this item. The MAPI Spooler has already begun transmitting this message.

Hari ini gue dapet permasalahan dari salah seorang user gue yang mengeluhkan bahwa email yang dikirim oleh beliau selalu tersangkut di outbox Microsoft Outlook. Sudah coba dilakukan penghapusan manual, selalu muncul error seperti “Can’t open this item. The MAPI Spooler has already begun transmitting this message.” dan akhirnya beliau meminta gue untuk hapus email tersebut.

Setelah gue coba googling, ternyata ada issue serupa yang pernah dilaporkan didalam situs msoutlook.info dan setelah gue coba, ternyata langsung berhasil. Berikut langsung gue copy dari situs itu.

QUESTION :
I have a message stuck in my Outbox (because it is to large to send). I tried to delete it but I get the following error;
“Can’t open this item. The MAPI Spooler has already begun transmitting this message.”
How can I get rid of this message?
ANSWER :
1. Place Outlook in Offline Mode;
     1.1 Outlook 2007 and previous
           1.1.1 File  -> Work Offline
     1.2 Outlook 2010
           1.1.2 tab Send/Receive-> button Work Offline
2. Close Outlook.
3. Verify in Task Manager (CTRL+SHIFT+ESC) that the outlook.exe process is no longer listed on the Processes tab.
4. Start Outlook again.
5. Double click the message in Outbox to open it in its own window.
6. Either delete it, move it to the Drafts folder or remove its attachments and send it again.
7. Put Outlook back on-line by disabling File-> Work Offline
8. Press the Send/Receive button.