Re: Mysql & amavisd-new
Yep, the config I'm using at the moment (as in the block diagram) does use amavisd-new, which is what summons ClamAV as well.
I did install Postfix with MySQL compiled in, and used that in a previous iteration of the system when I provided a load of mail aliases for a client, and it was easiest to tweak them that way. Now I have far fewer, so they're all in the text file instead. Space permitting, however, I will include notes on how you can use a database to handle one of your domains.