From a security standpoint, and from wanting to run a secure mail server for 2 domains, it would allow for the general case of user connecting directly to one citadel machine or the other, and being able to have the two machines talk to each other (even using standard SMTP if need be) to be able to deliver mail to the other domain / citadel box without having a flood of attempted connections from other machines wanting to relay to that domain.
My use case is more in the realm of keeping the local users as local users, with the exception of citadel being able to mail to a different citadel (with the same local users) and be able to deny outside email if not coming from an authenticated user. So basically to handle the communication between the two servers, and reduce the visibility otherwise. In essence, close port 25, unless the magic packet comes, and then only for that connection open it, and then close the port again. My clients all use non-standard ports for IMAPS and SMTPS, so that is fine, but to facilitate normal routing of mail to the other domain, it would basically mean dead connection / server not found if the connection is not coming from the known machine (although I guess I could do that with firewall rules on both sides as well...)
I guess I just thought it was a neat idea, but I guess we all think our ideas are neat... until smashed down, trampled on, etc. (not saying that is how I feel...)
Perhaps I misunderstood your intent to phase out intercitadel networking and clustering.
