A reader was concerned that Outlook taken over by a virus as it was trying to send out messages from Outbox though the Outbox was empty.
It's not a virus, but a stuck read receipt. For some reason, the SMTP server won't accept it but Outlook keeps trying to send it. Read receipts are stored as hidden messages in the mailbox and you'll either need to configure Outlook to use a SMTP server that will accept the receipts or delete them using MFCMAPI.
If you are using an IMAP account and getting NDRs for read receipts, see Outlook is Sending Unknown Messages
After deleting receipts several times, the user asked how to prevent the problem from recurring.
To avoid stuck read receipts, you'll need to configure Outlook to stop sending read receipts responses automatically or configure Outlook to always ask what to do. Although it's annoying to be asked if you want to send receipts, you will soon find out who requests receipts.
In Outlook 2007 and older, you'll find the option to disable read receipts in Tools, Options, Preferences, Email options, Tracking Options.
Send or delete stuck Read Receipts
There are two methods that can be used to get rid of read receipts:
- Change the SMTP server for the account to a SMTP that can send the receipt. After the read receipt is sent, change the SMTP back to the one you normally use for the account after they are sent.
- Delete the hidden messages using MFCMAPI.
Use MFCMAPI to Delete Stuck Read Receipts
Download and run MFCMAPI. Use the 32-bit version with Outlook 2007 and earlier or Outlook 32-bit. You need the 64-bit build when you installed the 64-bit version of Office or Outlook.
Note that MFCMAPI is updated frequently and these instructions and screenshots are from one of the older versions. The menus may not be identical, but the steps are the same: logon, find the default data file, locate the receipts and delete.
1. From the Session menu, choose Logon . Select your profile from the Choose Profile dialog.
When a secondary account has its own message store and places the outgoing messages in its own Outbox, select that account and right click, choose Open Store (or double click to open store).
Tip: you can right click on the account in the list and choose Open Store instead.
4. In the Contents table, right click a read receipt and choose Abort Submit. Ok the dialogs.
Repeat steps 4 and 5 for each read receipt you need to delete.
Note: Outlook Connector (Live/Hotmail/MSN) accounts do not return read receipts and you will not have any "stuck" receipts with these accounts.
Delete Read Receipts using MFCMAPI Video Tutorial
This video shows you how to delete read receipts using MFCMAPI.