Currently guys you have no other option than to switch off automatic mail scanning in the avast4.ini file and configure your accounts in the same way as in previous versions.
Well, this feature (automatic mail scanning) is here to make the configuration process easier. In fact, when you do nothing but install it, all your mail trafic will be protected. There shoud be no double scan, we just scan connections leaving you PC to the internet. Localhost connections are NOT scanned (like those between Outlook and MailWasher or K9) - unless explicitly configured (127.0.0.1 : 110, username#pop3.myisp.net)
And there are no guarantees that those 'safe' anti spam solutions are not exploitable with viruses as well. For example displaying images was for long considered safe but today we have exploits for JPG images too. You never know what is waiting in the 'RichText' component used by antispam to display plain text.
Anyway, when you have certain clients (eg. anti spam) which shouldn't be scanned and others which should it's better to stick with manual settings per mail account.
To switch off automatic mail scan, edit your avast4.ini file as follows:
[MailScanner]
AutoRedirect=0
Cheers
Lukas