Confusion about MX records

Question

I'm very confused by the fundamentals of DNS records (in this case MX records). Right now I have registered a domain name (let's call it example.com). This domain is configured to my linode's IP via their nameservers.

The default MX record that is in the Domain Manager is 'mail.example.com'. Fair enough.

I followed this tutorial about setting up a exim server.

Exim Tutorial in Linode Library

and I'm kind of confused. My default hostname on the machine is 'antares' and thus the FQDN is 'antares.example.com'. In this tutorial I don't see how this 'mail.example.com' is coming into play? Where do I specify this? Or should I point the mail MX record to antares.example.com?

I'm very new to DNS records and even more new to mail records. Any hints to clarify my misunderstanding would be invaluable.

Answer 1

the DNS server for your domain will by default serve up the www or .domain.com entry to web browsers etc but it actually hosts a bunch of name pointers for other services, one of which is mail exchange.

Services which need your mx record value know how to look it up from your DNS server, so in this case they will find mail.domain.com when you supply the domain.com part.

If you need to set up a mail server you will need to change the mx record in your domain manager to point to your machine ip, this can be different from your default www host name/ip on the same domain as every service can be served by a different host (any ip).