TCPView shows nothing unusual
Hmmm ... what is usual? It should at least look a little different with avast installed.
My friend Tech may not have mentioned that you should be looking for any processes that are linked to port 12025 (the ashMaiSv.exe listening port).
avast can log in more detail any connections made through the Internet Mail scanner to send or receive email.
You can get the mailscanner to log your connections by editing the avast4.ini file (in Program Files\Alwil Software\Avast4\DATA folder).
In the section headed:
[MailScanner]
add the line:
Log=20
and save the updated file.
The log will be in Program Files\Alwil Software\Avast4\DATA\log\ashmaisv.log
The log will show any connections being made on the email ports scanned by avast and the name of the process that is making the connection.
There is no harm in leaving the logging option set on in the avast4.ini. The log is cleared at each system restart so it will not build into a huge file and will have the information if the connection problem should happen again.