Different rewriting for To/cc headers?

[starke@unix.worldcom.com]

  Here's weird and convoluted problem that I need to get figure out before 
I can install zmailer.  I'm expecting a wild wade through source, but before
that I'm hoping someone here knows the solution, or has some ideas about it.
Basically, I'm trying to rewrite cc: header addresses differently than the
To: header.

THE SETUP
We route mail for our customers to the Internet, and have Internet
domains registered for them, so when they send mail, it gets converted from
their ugly internal address to their nice Internet address.

THE PROBLEM
If an internal person sends mail to an Internet user, and cc's a person in 
their company, the Internet person sees a header like this:

From: <sender's Internet address>		# converted from ugly version
To: <Internet recipient>
cc: <cc's ugly internal address>		# not converted

We treat sender & recipient addresses differently, since we make changes
in both directions.  However, we want the Internet recipient to see the 
Internet address for the sender and all recipients.

THE SOLUTION
Well, I don't have one, but here's how I see it.  If I'm looking at a 
recipient header (a cc: header, which means it is different than the 
envelope), and the recipient envelope is going to the Internet, 
then I do conversions on this cc: address as if it was the sender.

Have I made any sense?  Any constructive suggestions would be gladly 
welcomed.

thanks
Sean

-- 
Sean Starke <starke@worldcom.com>                       (713) 650-6522 x42
WorldCom System Administrator
Wolf Communications, Houston, TX           http://www.worldcom.com/~starke