So, in short, the avast mail scanner doesn’t support SSL (it has never had).
- interception of the traffic by avast
- actual scanning of the traffic
Unchecking the SMTP box in Internet Mail provider’s settings disables 2 but not 1.
To prevent avast from doing 1 (which makes sense in your case as you’re using SSL), please open the file \data\avast4.ini, and to the [MailScanner] section, add the following line:
StartSMTP=0
Besides using MS Outllook (not Express) and The Bat! for SSL, here is a workaround for SSL and POP3 accounts:
http://forum.avast.com/index.php?board=2;action=display;threadid=8775
to use SSL with other clients and also have the protection of avast.