MX DNS one IP two domains

Question

I have two domains: 'example.com' and 'elpmaxe.org' and a server - 'server.example.com'

At the moment the mail for 'example.com' is hosted elsewhere so I have set up postfix, dovecot etc to be able to host email on two domains. The setup seems fine with local command line testing.

So I have two mx records on 'example.com' pointing to hosted mail servers elsewhere which i want to eventually delete.

I have an A record pointing to 123.456.123.456 (server.example.com) on both DNS zones 'example.com' and 'elpmaxe.org' and I did have a 'mail.example.com' MX record pointing to server.example.com ip address until i changed the FQDN to server.example.com

Now I have added an MX record to example.org to point to server.example.com (can I add an A record - server.example.com.example.org(??))

I can't now add an MX record on example.com to point to server.example.com

If i dig mx server.example.com it is not showing anything - its only been a couple of hours maybe it needs time to propogate.

so DNS zone 'example.com'

@               IN  300 A   0.0.0.0
@               IN  300 MX  10 mail.example.com.
@               IN  300 MX  20 mail2.example.com.

www             IN  300 A   1.2.3.4   #(server.example.com)

mail            IN  300 A   5.6.7.8
mail2           IN  300 A   9.10.11.12

DNS zone 'elpmaxe.org'

@               IN  3600    A   1.2.3.4   #(server.example.com)
@               IN  3600    MX  10 server.example.com


mail            IN  3600    A   1.2.3.4
www             IN  3600    A   1.2.3.4

Can anyone tell me what I am doing wrong here?

Answer 1

There seems to be a degree of misunderstanding about the function of MX records, but in essence the problem seems to be that although the MX record for elpmaxe.org points to server.example.com, there's no A record for server.example.com.

I think if in the zonefile for example.com you define an A record for server.example.com pointing to 1.2.3.4, then mail for elpmaxe.org should start going to your new server. If in addition you change the MX record for example.com to server.example.com and remove the two existing MX records, then mail for example.com should also start going to your new server.

You don't need an MX record for server.example.com.

In addition, may I encourage you not to redact the domains in questions like this one? When investigating the DNS, it's often very helpful to know the real domains, and it can sometimes be impossible to solve if the real data are not given - see this question and answer for an example.