I got the split domain setup working so that i will not have any delivery loops. However when it does not know of an address it returns the following error to the sender.
550 5.7.1 <email@example.com>: Relay access denied.
My setup is like this for the domain.
Mail -> Rackspace cloud (split Domain setup) -> zimbra
I would like to make it so that if Zimbra gets the message it knows The box is not at rackspace it returns the user message for something like "User User here by" or etc.
If people get Relay Access Denied they will assume its a problem wiht us when its the mailbox is not valid