I have seen that in the past when the authentication details (user name and password, or lack of them result in you sending mail when not logged in. The server then considers one too many as you are not logged it. Check the outgoing server (SMTP setting for the account and ensure they are correct. You make no mention of what mail provider, so I can not look them up for you, but they should be published on their web site. Note there are very very few SMTP servers that do not require authentication. So a Setting on None is almost certain to by wrong.