Not a bug per se, but just a note for possible improvement.
Currently, an outgoing email failing 5 times is marked with dontSend and is ignored during any transmitMessages action. This situation can happen when for instance login is failing because of outdated credentials, or mistyped attempts... Then the email stays in the out going mail folder and don't react to any sending action, leaving the user wondering what happened.
Possible improvement may include to mark email only for sending issue and not any other kind of issue during the transmitMessage action.