canonical address for calendar invites

[SalmonsSteve]

I have a production server with a local domain (domain.local). During initial setup the server was set to catch all emails originating from domain.local and rewrite the address to domain.com. This works great for all emails coming from users of both the web interface and zimbra desktop. Where I run into a problem is calendar invites sent to people outside of my organization. domain.local never gets rewritten so the invited party, upon acceptance of an invitation, sends the acceptance to user@domain.local instead of user@domain.com. Is there a way to rewrite the canonical address for the sender of calendar invitations?