Multiple MX entries

[emmanuel]

Actually not sure if this should belong in DNS or Email but this seems more appropriate.

I'm trying to figure out a clean way to migrate my client on an existing server to a new server without them losing their emails.

Their email clients are all set to check emails from pop3.somedomain.com or mail.somedomain.com due to some legacy settings so it's not uniform.

So I thought of manipulating the my DNS records record to do the switchover without losing emails.
Using 123.123.123.123 as dummy address for existing server and 111.111.111.111 as new.

mail 60 IN A 123.123.123.123
pop3 60 IN A 123.123.123.123

the existing MX record is
somedomain.com 60 IN MX 10 mail

I added
somedomain.com 60 in MX 0 newmail
newmail 60 in A 111.111.111.111

This should in theory cause all new mails to be sent to the new server since newmail has a preference of 0.

But my client's staff will still be checking the older server and clearing it of any existing emails when they get back to work in the morning since mail/pop3 are still pointing to the old address.

Subsequently, after my client's contact confirms they have cleared their emails I can then set mail/pop3 to point to 111.111.111.111
Since the TTL is currently 60, within 1 minute, they should be checking emails on the new server with minimum disruption or email losses.

However, when I try this out, sending emails to [email protected], which exists on both old and new server, will result in

<[email protected]>
111.111.111.111 does not like recipient.
Remote Host said: 550 Authentication required.
Giving up on 111.111.111.111

The question is therefore, why doesn't this work? The correct mail server 111.111.111.111 is being used, the account exists.

In additional, isn't the smtp server supposed to try the next MX server if the first cannot be delivered?

 

[nobaloney]

The problem appears to be that the mailuser isn't set up right on the server with ip# 111.111.111.111.

SMTP will only try the next server if the first server doesn't answer, not if it sends back an error.

Jeff

 

[emmanuel]

The problem appears to be that the mailuser isn't set up right on the server with ip# 111.111.111.111.

Ah damn me, I manually removed somedomain.com from /etc/virtual/domains because earlier during testing, it kept doing local deliveries from another active domain to somedomain.com.

Thanks for the reminder! Fixed that and it works as expected now!