[cobalt-users] RaQ4/RaQ550: Shunting mail around with MX rules and sendmail

["Michelle A. Hoyle" <mahlist@xxxxxxxxxxxxx>]

Summary:
We're moving a high-volume mail domain from the RaQ4 to the RaQ550 
which involves an IP change.  We want to ensure that no mail is lost 
or stuck on the old machine.  How can we do this?


Detailed Discussion:
We currently host a high-volume mail/web site on our RaQ4, but due to 
problems with the network interface constantly thinking the network 
doesn't exist, we're moving it from the RaQ4 to our RaQ550.  The two 
machines have a different block of IPs assigned to them, so we will 
be changing the IP address.   Prior to actually doing this move, I've 
been experimenting with a domain which does not any active user 
e-mail accounts (seejapan.co.uk).

I have the following MX rules set up on the DNS server (not managed 
via the RaQ itself):

    * mail for seejapan.co.uk is delivered to raq550 with a preference of 5
    * mail for seejapan.co.uk is delivered to raq4 with a preference of 10


These MX rules force mail to be delivered to the RaQ550 which isn't 
currently handling mail for that domain because the domain hasn't 
been moved over.  I want the RaQ550 then to try to deliver the mail 
to the next MX server in the list (the RaQ4) where e-mail is still 
being handled.  Then, on the day that I'm actually doing the 
changeover, the RaQ550 would now be accepting mail for that domain 
(and mail would go there first) where it would be kept.  Then mail on 
the old machine could be forwarded back to the new machine using I 
don't know what.

I suspect there's a better way to do this -- one which might actually 
work.  How do other people do this so that you don't end up with mail 
on the old machine that hasn't been POPped yet?

I could tell everybody to POP it using the RaQ4 name and the switch 
to the RaQ550 name later, but I'd rather keep them using 
mail.seejapan.co.uk (for example) which has an A record to the 
appropriate RaQ.

Thanks,

Michelle