Mail with attached video stuck in iPhone Outbox.

Troy29 posted this and it worked.

I know this thread is a bit old, but just in case anyone finds it here is the solution:

1) Put the iPhone in Airplane mode

2) Open the Mail app

3) Go to the Outbox

4) Click Edit, click the circle next to the stuck message to select it

5) Click Delete

6) Take the iPhone out of Airplane mode

7) Return to the Mail app. :-)