I don't have the "Mail Shield" installed. When I open Settings, there's no Mail Shield options. Someone said that this wording has been inserted into outgoing e-mails for the past several Avast versions. I often Blind Courtesy Copy (BCC:) myself into e-mails I send, but I've never seen the "This Computer is Guaranteed to be Virus Free by AVAST" wording before this month's update.
Anyway, since I'm using the FREE version, my leverage on this issue is extremely limited. So I'll just register this as formal user complaint, and move on. Thanks to everyone for your input and suggestions!
-Allen