Quote from the Split Domain instructions:
# The primary MTA must
* be aware of, and accept mail for, all accounts on the domain
* reject on RCPT TO: those accounts that do not exist in either system
* forward mail to the secondary MTA for users hosted there.
Primary Mail Server Details:
  • Debian 4
  • Exim
  • Courier-Imap
  • MailScanner
  • Iptables
  • Webmin
  • On DMZ behind firewall

Secondary Zimbra Test Server:
  • Ubuntu 7.10 (6.06 will not work do to Grub issue on this test box)
  • P4 2.0ghz, 1.5gb RAM, 160gb HD, CD-ROM
  • Zimbra NE 5.05 60 trial (downloaded 5/1/08)
  • Also on DMZ

Network Layout:
  • Internet via ISP router -> WAN (Sonicwall firewall appliance)
  • DMZ -> switch -> debian and zimbra (direct internet IP's)
  • LAN -> 192.168.xxx.xxx

How do I make the primary mailserver aware of the new Zimbra secondary mail server? What do I need to do so that it knows what users I move or better yet, new users I create, on the new Zimbra system?

Any help would be appreciated. I think I have Zimbra set up according to the split domain instructions, but I'm not sure.

~ Culley