Hold your horses.
Lee mixed up a few things.
Authentication is something else as SSL.
Avast is perfectly capable of handling smtp servers that requires authentication.
- Make sure no email client is opened.
- Reset avast4.ini [mailscanner] section to it's default.
- Setup the mail as if Avast isn't there.
Test the mail. If you get an error let us know which one.
If this doesn't allow you to use the mail:
Setup the mail manually as explained
HERETest the mail. Let us know what happens.
Make sure that Avast is allowed in your firewall.