I have Zimbra 5.011GA up and running on an RHEL5 system and ultimately, I'm hoping to migrate users from an Exchange 2003 system to Zimbra in a split-domain configuration. I prefer to have Zimbra as the authoritative server and I've found some documentation for this configuration, but my migration hasn't progressed that far yet. Currently, I'm slightly confused with the DNS configuration, specifically, the MX record. Our LAN is using Win2k3 DNS server with one master zone (FQDN i.e. local.domain.com) which works just fine for Exchange server. I followed the installation documentation and I specified the FQDN of the server in /etc/hosts, and the server name appears to be correct (i.e. zimbraserver.local.domain.com).
On the Windows DNS server, I created a second MX record with a higher priority just for the Zimbra installation, but I noticed that specifying the FQDN during the Zimbra installation results in the domain being specified as the FQDN once the installation is complete (i.e. email@example.com instead of firstname.lastname@example.org). Deleting the domain after the installation is completed and adding the correct domain does seem to ostensibly correct the domain naming issue, but I'm concerned that mail will not properly be delivered, especially mail sent to and from the Exchange server and inbound mail from the Internet.
I realize I could create another master zone on the Windows server (i.e. domain.com), but my understanding is that this is not advisable because our ISP/hosting service (and I suspect most ISPS or hosting services) defines an MX record for our domain (i.e. MX record for domain.com which points to our firewall). Has anyone else run into a similar DNS configuration dilemma?