Sendmail "To:" header rewriting

["Sean Enraght-Moony" <sean@xxxxxxxxx>]

I know there are some sendmail fundis on the list, so please forgive the 
slightly off-topic question.

Say I have a mail server, called mail.domain.co.za on a LAN, running 
sendmail.  To the worst of my knowledge, this is 8.9.  The real 
domain.co.za server is sitting at the other end of a 64k line.  I'm using Exim 
on the (virtual) domain.co.za server to forward mail to mail.domain.co.za, 
and people on the LAN fetch their mail from mail.domain.co.za.

I'm anticipating quite a lot of internal (to the LAN) email, so I want email 
sent from somebody@xxxxxxxxxxxx to otherbody@xxxxxxxxxxxx to really 
go to otherbody@xxxxxxxxxxxxxxxxx, thus avoiding the bounce up and 
down the 64k line.  I'm finding the sendmail online technobabble very trying. 
In fact, I'd like to nominate sendmail for the obfusticated code top 10 list of 
all-time.

Is there a simple way for me to rewrite the "To:" header so that I can 
achieve ther above for outgoing mail?

This scenario is duplicated several times, and is likely to be duplicated 
more and more, so I'm looking for a solution that Senior El Grande Stupido 
here can understand and implement.  I'm sure it must be something simple.

Gracias
Sr EG Stupido, SAB and bar

------------------
Sean Enraght-Moony
Flavour of the month nominee, May 1976
Management Information Planning
Johannesburg, South Africa
sean@xxxxxxxxxxxxxxxx
http://www.mip-holdings.com
Time flies like an arrow. Fruit flies like a banana.
  -- Groucho Marx