I have got zimbra listening on port 81 so things happily co-exist with apache. I have set the mta to listen on port 26 so exim starts great. I've got exim to forward mails to port 26 and zimbra picks it up. The last bit has got me stumped. When I set the "Relay MTA for external delivery" to localhost:25 the mail goes into a queue with the error "mail loops back to myself". But that's what I want it to do, loop back to localhost but on port 25 so exim can pick it up and deal with it. I have to use exim, it is doing really useful stuff that isn't available with zimbra. My main customer is a big company and can have another mta so there isn't a problem but all my other customers can't justify two mail servers, they aren't big enough so I can't use zimbra with them unless I can get it running with exim on the same server. I'd be well happy if someone could help me out.