Set outgoing IP address based on sender e-mail address?

[Nate Carlson]

Hey all,

Sorry if this is a FAQ, I can't find anything about it online.
Is it possible to set the outgoing IP address of a locally-generated 
message based on the sender's e-mail address?

IE, if a message is submitted via 'pickup' with the sender address of 
'u...@example1.com', use the IP '192.168.100.10' for the outgoing IP 
address.

If a message is submitted via 'pickup' with the sender address of 
'u...@example2.com', use the IP '192.16.100.11' for the outgoing IP 
address.

Basically, in a virtual hosting environment, I'd like to ensure that mail 
sent via one user cannot affect another user's IP's 'reputation', and I'd 
also like the outgoing mail server to match the incoming MX record for the 
domain.

Thanks!

-Nate