Is there an AVAST! setting which will avoid the avast! messages in the header, e.g.?
X-Antivirus: avast! (VPS 080529-1, 05/29/2008), Outbound message
X-Antivirus-Status: Clean
X-Antivirus: avast! (VPS 080529-1, 05/29/2008), Inbound message
X-Antivirus-Status: Clean