email forwarding setup

[Simon Buchanan <nmc@orcon.net.nz>]

Hi There, postfix with amavis and dbamil on debian.

I have everthing sorted, but now need to have clients setup some 
forwading mail addresses... example is this:

user1@example.com => delivery to user1 (dbmail box)
user2@example.com => devliery to user2 (dbmail box)
user3@example.com => forward to user@external-example.com (no dbmail box)

I have everything other config im mysql and would like to be able to set 
this up in mysql as well... Where do i do this? do i have postfix do it? 
, amavis do it? or dbmail?

Regards,

Simon