What email doesn't use SSL?
If Avast email protection only works on non SSL isn't that like almost none that it works on?
For sure not...
A lot of servers do not use SSL. Even when using, if you install Stunnel you can manage them, both inbound and outbound email scanned.
One of my accounts is GMail and it's being scanning while receiving and sending... No trouble.
Excuse my ignorance but it seems to me that an email is just a another file why couldn't it be scanned?
Gmail uses SSL (Secure Socket Layer) connections. Avast mail scanner doesn't support SSL (Secure Socket Layer) connections.
But take a look here:
http://forum.avast.com/index.php?topic=10428.0 to see how to set up secure email with avast!.
Since SSL/TLS e-mail is encrypted and decrypted in the client, external virus scanners (including avast!) can't read or scan it.
The solution is to pass e-mail in and out un-encrypted from your client (Outlook Express, Thunderbird, ...) to a proxy program (Stunnel) that does the actual ssl or tls encryption/decryption of the pop3/smtp e-mail and communicates directly with the ISP server on the appropriate ports. Another drivers (OpenSSL) are need as a library of encryption/decryption routines. Stunnel now comes as an installer which installs Open SSL and Stunnel so now you just have to download the installer version from here
http://www.stunnel.org/download/binaries.html