Yes, immediate--immediate loss (rejection) of one TTL's worth of mail at minimum. That's unacceptable customer service.
The MX algorithm is simple and effective, try to understand how it applies to overcoming EXACTLY this switchover phase, which is nothing but the primary MX being unreachable. Imail may not be amenable, but since you're the Best Damn Imail Expert Ever, I'm sure you can figure out something. I, Imail dumbkopf, make a humble suggestion below.
With IMail (or any other virtual hosting product), incoming mail for an outdated domain on a server that accepts mail for other domains (and thus must still be listening on 25) will be rejected unless other precautions (a store-and-forward mailroute or other preparation) are taken.
The simple solution here is to have the Imail server return a 4xx after the:
RCPT TO: [EMAIL PROTECTED]
Since Imail doesn't have that unix-MTA flexibility, here's a solution (to be tested):
At the point of switchover, point the virtual domain's mailbox storage path on the current Imail box to a (tiny) partition that is FULL, so every Imail attempt to receive mail, for that single virtual domain, will cause Imail to try to accept the mail (it is still an Imail domain) but return a 4xx "mailbox full" or whatever, immediately refusing/deferring all incoming mail but only for the virtual domain.
Copy the domain's mailboxes to new box.
Start the domain on the new box.
(at some point, no hurry, when no more mail arrives at the old server, delete the old virtual domain and its mbx storage)
Looking from the Intnernet POV at the above, the sending MTA sees the "4xx mailbox full" transient rejection and goes into defer/retry mode, during which time, 15 minutes or less?, the A record for the MX hostname expires from the sending MTA's DNS cache, and its next attempt to deliver the deferred msg will be to the new IP address. No mail "lost", no forwarding BS, etc, etc. No duplicate mailboxes, no parallel service, no futzing with forwarding, totally transparent as possible to Internet senders, and totally transparent to Imail users.
Len
_____________________________________________________________________ http://IMGate.MEIway.com : free anti-spam gateway, runs on 1000's of sites
To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
