Email Gateway solution

[Steve Buehler]

I have posted something similar here before, but need something a 
little different.  I have posted this to the comp.mail.sendmail 
newsgroup also.  Hopefully I will get a response between these two 
resources.  I am using RHEL AS 4 as a mail gateway that I am trying to setup.

I am trying to setup a mail gateway using Sendmail.  We have a 
server2 (with 200 domains) that we would like to lighten the load on 
by having all outgoing mail go through a mail gateway for virus 
checking.  This is already working.  Running SpamAssassin, 
MailScanner and ClamAV along with all of the websites really slows 
things down and that is why we are wanting to do this.  What I now 
want to do is to setup the mail gateway as the incoming mail server 
for all domains on server2, virus and spam check the emails, then 
send them on to server2 for local delivery.  I don't know how to set 
this part up and was hoping somebody here could help me.  I can setup 
the MX records to point to the gateway, but don't know how to setup 
the gateway to send all of the mail onto server2 after checking for 
spam and viruses.

I know of one company that has a series of mail servers.  server1 
receives all incoming mail and checks for spam deleting any 
spam.  Then it sends it to server2 which checks for viruses and 
deletes them when found.  Then it sends it to server3 for pickup by 
the clients.  Of course they won't tell me their setup, but they will 
do the setup on my server for a very LARGE fee.  About $3,000.  I 
could setup a separate email server altogether for that.  The problem 
is our control panel, Ensim.  So to keep from having to teach our 
clients how to use a separate server to send and receive email on, it 
would be easier if we can do it without their knowledge in the background.

Any help would be appreciated.
Thanks
Steve