Port:110
Are you sure?
Sure. WebMail addon on Thunderbird requires fewer teaks compared with stunnel. Now I forgot to point out that WebMail doesn't need the special port configuration after commas in Tech's screen shot. Tech is using stunnel. However, it is necessary to let it watch local traffic by unchecking the "ignore local connection" setting whether we are using WebMail addon or stunnel.
That said, I'd rather be happier with Thunderbird + Gmail IMAPs + stunnel. We can make full use of Gmail's functions, especially the spam filter through IMAPs, too.
Take a look here: http://forum.avast.com/index.php?topic=10428.0 to see how to set up secure email with avast!.
This thread have links to more recent two threads, in both of which you are involved, with more updated info. Stunnel installation is not so difficult if may be bit confusing and once it's set, we can forget about it. WebMail addon has its special benefit such as making Thunderbird usable even under tight firewalls.