On Monday 24 November 2003 8:21 am in comp.sys.sun.admin Dusan wrote:

> 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 (sol9), 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@ourdomain.sk it will go directly to maiold and when sending to
> johnthomas@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

No in the above case all mail will go to mailold unless mailnew
goes offline.
Mail addressed to johnthomas will be rejected <user unknown>

The lowest number MX takes preference.
The MX system only looks at the domain.
The mailbox name is only examined by the destination system.

Reduce the TTL of your DNS to 1 hour at twice the existing TTL
in advance.
Set up mailnew with a full set of new user accounts.
Set up aliases on mailnew for the old accounts.
Set the MX of mailnew to 5 .
All new mail will now go to mailnew when DNS has propagated.
If you want to keep mailold as a standby machine, fixup the
accounts as above, otherwise take it offline after mailboxes
have drained or been moven to mailnew.

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