MailShield, secure connections, & certificate checking

I temporarily configured avast 6 to scan email to/from a server I haven’t used for ages. MailShield was configured to translate 110 to POP3 on 995 via SSL, and 25 to SMTP on 465 via TLS. Secure communications appear to have been established, but at no time did I receive any prompts regarding the self-signed certificates used by the remote server in question. I found this odd for several reasons: 1) I doubt I ever before configured avast to access either the POP3 or SMTP account and thus I doubt I ever before told avast to accept self-signed certificates from this server, 2) the certificate associated with POP3 995 SSL was regenerated just moments before I set this up, so even if I might have accepted a self-signed certificate in the distant past avast would have seen a newer and different one, 3) The SMTP self-signed certificate very recently expired, so even if I had previously told avast to accept one in the past there is something to be said for avast warning me about the recent expiration.

All combined, this makes me question if avast (6, and possibly 7?) MailShield is checking certificates as it should be. Is this a known shortcoming or is there something I need to check on my end?