Two mail servers on the same domain

[Dusan]

"Chris" <chris at nospam.com> wrote in message news:<bptfaa$122q$1 at sf1.isc.org>...
> "Dusan" <dkulisie at truni.sk> wrote in message
> news:bptdna$1062$1 at sf1.isc.org...
> > Dear all,
> > this is a quite newbie question, I think :)
> > We have an old mail server with about 200 users mail accounts.
> > We want to exchange it for the new one, and we are planning to use
> > following method, which we don't know if it would be correct.
> > We want to install a new machine on the same domain and to configure
> > mail there (postfix).
> > For example a user John Thomas has an account "jthomas" on the old
> > mail server. We would make a new account "johnthomas" on the new
> > running mail server.
> > In the DNS server we would have
> > ourdomain.sk  IN  MX 10 mailold.ourdomain.sk.
> >               IN  MX 20 mailnew.ourdoamin.sk.
> > So our reasoning is that in the case somebody sends an email to
> > jthomas at ourdomain.sk it will go directly to maiold and when sending to
> > johnthomas at ourdomain.sk it will go to the mailnew.
> > By this method we would create all accounts in the new manner...
> > Is this correct ?
> > And in the case it is not, how this should be done ?
> > Thank in advance for your advice
> > Regards
> > Dusan
> >
> When sending an email to a domain the only thing that matters as far as DNS
> resolution is concerned is the bit after the '@'. So, it doesn't matter if
> the mail is for jthomas at ourdomain.sk , johnthomas at ourdomain.sk or
> mickeymouse at ourdomain.com. In all cases mail will be delivered to the
> primary MX record, in your example mailold.ourdomain.sk.
> 
> The best way would simply be to create the same accounts on the new server
> and maybe alias some names to the new format if that is what you wish to use
> and then simply swap the box out one night for the new one.

that's exactly what we intend to do.

> 
> Chris.