Question details:

There is a document in my outbox that won't email. A fellow employee tried sending a video from my email to hers but it just keeps hanging there in the Outbox and won't go away. I tried deleting it but it just says "cannot open this file Outlook has already begun transmitting."

Answer:

Try this solutions:

1. Try to delete and recreate the problematic account, and try again.

2. Uncheck all add-ins and try again.

3. Close Outlook, search for and rename the outcmd.dat and extend.dat files, and try again.

or this one( problem could be caused by an invalid email address):

1. Open PostCastServer
2. Click Settings
3. Change the Mail Send Frequency from x to MANUAL and click OK.
3. Take a note of the email address at fault
4. Right click the message that is stuck and delete it
5. Click settings
6. Change the MANUAL back to immediate or what it was before.
7. Close PostCastServer window
8. Find the email address in Outlook and CORRECT IT.