outgoing mails from Thunderbird to gmail - AVAST!

Outgoing mails were getting an error 5.7.0 Must issue a STARTTLS... though the TLS settings were set correctly. Googling found this page which gave the solution of disabling AVAST scanning of outgoing emails. On my system, Avast 4.8 Pro, in the Enhanced Interface (as against the Simple Interface) it was in Tasks -> Resident Protection (right-click) -> Properties (it gives a warning at this point) -> Internet Mail (with the Advanced configuration checkbox at the bottom checked) -> SMTP -> Scan outbound mail. Removed it, and SMTP started working again.