alanrf
21
As you have probably guessed - you have found it.
You did mention earlier that you user Tor/Vidalia as a web anonymizer. I guess I should not have made assumptions about how Tor works.
Tor operates a bit like P2P clients, the folks who run Tor servers decide what port they will listen on and (as often happens with P2P) they choose a well-known email port since they know the server will not be running as an email server and the port will work for them. They then tell Tor users to connect to their server on that well-known port. This is, of course, all under the covers to you and so once in a while you connect to a Tor server on a port that is monitored by the avast Internet Mail Scanner and it shows up in the systray. It most likely also disrupts the Tor connection that is being attempted.
The solution is to edit the avast4.ini file and in the section headed:
[MailScanner]
add a line:
IgnoreProcess=tor.exe
avast will then ignore use of the ports it intercepts when made by Tor.
I will also drop a note to the avast team suggesting that they add Tor to their list of automatic exclusions so that the next Tor user along doesn’t have to work out the issue again.