One thing that I did want to say though is that when a virus is found and the option to send it to Avast is there, the file and a note, it doesn't go through MAPI at all, this is what happens everytime. Is this address still the correct one?
"Your message did not reach some or all of the intended recipients."
Subject: avast!
Sent: 11/2/2007 6:38 PM
The following recipient(s) cannot be reached:
'virus@avast.com' on 11/2/2007 6:38 PM
None of your e-mail accounts could send to this recipient.
That is weird as I can't send using SMTP only MAPI, but I never get any error like email accounts couldn't send to recipients.
I used to have similar errors not relating to sending to avast, but with a dial-up account if I tried to send an email where the account didn't match the ISP I had connected to, changing the From email address (email account) to match the ISP I was connected to resolved the problem.
The other aspect is if your email account requires authentication, that may cause the send to fail, but I'm not sure if this would give the same result. Check the SMTP settings match your default account in your email client.