This is the background: http://superuser.com/questions/400298/cause-of-intermittent-smtp-emailing-sending-problems
In short Outlook (2007 IIRC) was receiving the wrong IP address for the SMTP server domain - it turned out that the address was backwards. Any ideas why?
Using tcpview (from sysinternals) I saw that a SYN being sent by Outlook but no ACK. So then I ran a remote mtr to the SMTP server that showed no problems; then I ran a winmtr trace locally and found that there was a "blockage". That's when I noticed the addresses were different and that in fact instead of 80.x.y.10 the address being used was 10.y.x.80!! Weird. I've hacked a fix of specifying the server address in the hosts file.
I suspect a bug in Ad-aware Total (I'm not the sysadmin) that is taking the reverse-DNS address and truncating it; or at least something along those lines. The router is a Belkin N1. ISP is Claranet using PPPoE.