1. The avast Mail Shield should automatically setup your accounts info based on that of your Thunderbird email account settings.

  2. The MS Outlook email client also has its own avast plug-in, which means avast is essentially working from inside Outlook so the scanning happens before/after any encryption/decryption.

At least that is my understanding of the avast plug-in for MS Outlook. Since I don’t use either Outlook or Gmail I can’t test that.