.... iPhone message help?

[shykneejessie]

This message pops up when I try and send an email-it's always worked, why now? And how do I fix it?

It says: "A copy has been placed in your outbox. The sender address '[email protected]' was rejected by the server. "

 

[ImrantImmyt]

See if your putting the email address in correctly
Otherwise try using .com instead of .ca