It works just fine without avast. With avast & UseDefaultSmtp=0 Mozilla keeps prompting me for a password 2 seconds after I just entered it. And I know the password is right.

Setting use SSL to Never or When Available & Moz keeps prompting me for a password. Setting use SSL to Always & I get an error from Moz, “Sending of message failed. Unable to connect to SMTP server 127.0.0.1…” I also get this error after I hit cancel on the password prompt with use SSL at Never or When Available.