That makes me think about the setup in your email account. The fact that sympatico.ca is responding to this message with *nothing* is quite interesting.
I'd wander through the Avast settings to see if there's anything in there. Looking at the AVG settings on my machine, I'd disable the AVG Resident Shield and the Email Scanner to start with and see what happens. Nothing else should be blocking it.
You might want to pick up HiJack This (
www.merijn.org) to see what it finds. Note that it's geek-friendly, not user-friendly. It will give you lots of false positives... better than skipped negatives.