This split domain stuff has got me vexed. I've read through the Split Domain Wiki and have searched the forum for answers, but I'm still a bit confused.
What I can't seem to figure, is how this split domain works with my company's server configuration. We are currently working off of a Sendmail server, mail.genart.org. I need to migrate all of the accounts off of that Sendmail server to a Zimbra server which has just been setup. I can't move all of the accounts at once due to limited resources, so I plan to use the PST migration wizards once this split domain is accomplished. I would like to have a setup where e-mails come into either the Zimbra or Sendmail server and if the account and is not found are forwarded on to the other server.
To me, it looks like my only option is to have Zimbra configured as the primary e-mail server and to prescreen inbound e-mail on the Zimbra machine, forwarding them over if the accounts are not present. Is that assumption correct? If that is the case, what do I need to do to my MX records, Zimbra and Sendmail machines to make this work? Can I leave Sendmail as the primary server and tell it to forward e-mail traffic to the Zimbra box for those accounts which do not exist on the Sendmail server?
Thanks in advance for your help,