[b]SMTP Closing connection due to PassThrough[/b]
It means that mail scanner cannot scan mail because resident protection is not running. To prevent this, insert the line
PassThrough=1
to file C:\Program Files\ALWIL Software\Avast4\Data\Avast4.ini into section [MailScanner] and restart the process ashMaiSv.exe (or restart Windows). This allows your mail to pass through without scanning if resident protection is not running.
However if you wanted to scan your mail, you would have to let resident protection started and at least provider “Internet mail” running.