I have tried a few other AV products but now come back to bitdefender again.
One thing that i liked about a few competitor was that they added an footer to any outgoing emails sent from Thunderbird (in my case) with info that the email has been scanned with product ****** with AV database signature ****** and date ****** and so on.
I am currently running Bitdefender AV 2013 but have not found such an setting, even if it is setup to scan incoming and outgoing emails.