The new version of Avast has a MAJOR problem, the likes of which I've never encountered in 33 years of computing. I started getting "Permanent Error" bounce messages on any AOL email address put in the Bcc: box. My first thought was that it was AOL's fault, because they recently updated their software. But people in our development whose domain is aol.com were having not problems. Then I thought it was my email client, Windows Live Mail. So I tried sending emails to some AOL customers using Thunderbird, still putting the addresses in the Bcc: box. THEY ALSO BOUNCED. Tried sending emails to AOL customers using Comcast web mail, still putting the addresses in the Bcc: box. THEY DID NOT BOUNCE. It was only then I turned my attention to Avast. I had the option "scan outgoing emails" checked. I unchecked it, then tried again sending emails to AOL customers using the Bcc: box. THEY DID NOT BOUNCE!!!!! The odd thing about this is that if I put the addresses in the "To:" box, they go thru. In the Bcc: box, no.
Weirdest thing I've ever seen, but I've done enough experiments to know that Avast is causing the problem. How is a mystery, but it does exist. Is the Avast crew aware of this?