We've been running Zimbra 6 in a split domain configuration pretty successfully. The default domain is set to zhost.domainname.com, but our email addresses are primarily domainname.com.
To deal with this, I've made sure every account has a corresponding alias (e.g., email@example.com has alias firstname.lastname@example.org). Additionally, I set the Canonical Address in each account to email@example.com. This works great for most things (sending emails from external clients, the web client, and from Outlook 2007 using ZCO).
However, we've run into an issue I can't seem to resolve. When using Outlook 2007 to send invitations to external addresses, the meeting's organizer is listed as firstname.lastname@example.org, which unfortunately does not work outside our domain. I've tried various things to resolve this, like setting up separate personas or setting our gateway MTA to rewrite email addresses, but it looks like the organizer's address is separate from any email headers. There's got to be an easier way to deal with this than rewriting the body of the email.
I've tested this in the web client, and the meeting's organizer is correctly set to the address I specified in Canonical Address. This issue seems to be limited to Outlook using ZCO. Any help?