My SSL/TLS is bad?

When I start my Vista Windows Mail, it has recently has been warning me:

"Avast! has detected a secure connection from your mail program (process WinMail.exe) to SMTP server (

This type of connection cannot be checked for viruses. Please disable SSL/TLS in your mail client so that the Mail Scanner can scan your mail. The mail scanner will provide the SSL/TLS security itself."

Recently it has changed to :

"The server you are connected to is using a security certificate that could not be verified. The certificate's CN name does not match the passed value. Do you want to continue using this server?"

In both cases, when I click "Yes" my mail runs with no apparent problems.

Does anyone know what's going on, and how I can correct the issue? TIA, Paul