Support unencrypted mail relay

[mark-prins]

Trying to send mail via a relay that does not support SSL, gomail responds with unencrypted server and won't send.
There's a suggestion that sending without a username allows for unencrypted mail relays.

If this does work - add an 'anonymous' checkbox to the config page, and enable Save when this is checked and the username is blank. If anonymous is checked, set the 'from' property but do not send username or password.