Yes, having the IMAP server access the data directly on its local disk rather than using NFS is a big win. We gave up on NFS about 10 years ago.
How to set up referrals depends upon your server implementation. UW imapd inherits all system management from the underlying UNIX system. Since UNIX doesn't have referrals built in, that means that any sort of mechanism is part of your homebrew accounting system. Thus the answer is "you write code that latches into your accounting system, and you attach it to UW imapd code at such-and-such place." I'll be happy to provide details of the attachment (the hooks are there) offline. In some other servers, such as modern versions of Cyrus, referrals are part of the functionality of the server. However, note that login referrals are not widely implemented by clients. Pine implements them; I don't know about any other client. Apparently the Cyrus crew doesn't feel (or at least this is what I sensed during our discussions at the last IETF) that login referrals are particularly important compared to mailbox referrals. I'll let them speak for themselves. What we do is have a special DNS zone, *.deskmail.washington.edu, in which each user has his own DNS name in this zone. The machine in our IMAP server farm that serves user "mrc" is "mrc.deskmail.washington.edu". That machine may change from day to day, but I don't worry about that; I always connect to the "mrc.deskmail.washington.edu" system and it gets me to the right place. The zone is maintained through our homebrew accounting system. The advantage to this is that it works with all clients, not just those which know about referrals. Other sites have done the same thing, and it works well for them too. -- Mark -- http://staff.washington.edu/mrc Science does not emerge from voting, party politics, or public debate. Si vis pacem, para bellum.
