This one doesn't use SSL at 465, it's STARTTLS with either port 25 or 587.
@dosser -- please try "STARTTLS" + port 587.
If doesn't help, please try removing the domain from your login on the outgoing server settings screen -- i.e. change "user@a1net" to "user".
If that doesn't help either, please post the exact, complete, error message -- a screenshot would be perfect.