We have an old Mac OS X mail server that we plan to replace with a new Zimbra server, but we can't move all mailboxes over in one go, instead, we plan to route all internet mail to our new Zimbra server, which has the authoritative list of all users on the domain and can thus reject non-existent recipients.
Mail to valid recipients are then either delivered to the mailbox on the Zimbra server itself, or passed on to the Mac OS X server for those mailboxes still located there. The old Mac OS X server thus needs to be set up to accept all mail allegedly on the domain and pass it on to the Zimbra server in case it doesn't know about that particular user as explained here: https://wiki.zimbra.com/wiki/Split_Domain After reading through loads of postfix documentation, it seems like the thing to do is to edit /etc/postfix/main.cf on the old Mac OS X server and add in the following line before reloading postfix: fallback_transport = smtp:new.zimbra.server.com Does above seem correct? Is anything else required to make it work? Does below need changing? local_recipient_maps = proxy:unix:passwd.byname $alias_maps
