How to cancel an outgoing message

Go to your outbox folder, and then do a swipe left with your finger near where the date of the email is listed, and then a delete (in red) should show up and then touch the delete to delete the outgoing message.
hope that helps 🙂

Are you looking on the screen that lists the folders, like Inbox, Drafts, Sent Mail, etc? If there is not an email that is waiting/trying to be sent, the Outbox does not show up. But if there is an email that can't be sent or is in process of being sent, the Outbox shows up. (I just put my iPhone on Airplane mode with wifi off, to test it out, creating an email and clicking on send)

well i dont see an outbox folder in either of my email accounts on my i phone..gmail or yahoo...the video email is stuck and i cant stop itfrom being sent all the time!!!

Try this: Put the phone in airplane mode, send another message, your outbox should appear now, delete both messages, then turn airplane mode off.