====== DNS records ======

[[http://gogs.info/books/debian-mail/|This article is outdated. Updated version on building a mail server on Debian 6 is published as a free eBook here.]]

Note: Server in this example is named atlantis.example.com. 

First, we need to check our hostname

  atlantis:~# hostname -f
  atlantis.diabmon.com

If hostname did not return FQDN of your server edit ''/etc/hosts''. You should see something like this, if not, change according to your IP address and server name.

  127.0.0.1         localhost
  YOUR-IP-ADDRESS   atlantis.example.com    atlantis

Now check your ''/etc/hostname'' file:

  atlantis.example.com

Change the names to match your server name and reboot the server. Run ''hostname -f'' again and you should see ''atlantis.example.com''.

Now, we need to check that our DNS servers have an MX record for our example.com domain. Install DNS utilities:

  apt-get install dnsutils

We are going to use ''host'' to check information about our domain:

  atlantis:~# host example.com
  example.com has address YOUR-IP-ADDRESS
  example.com mail is handled by 0 mail.example.com.

We can see, that the mail for our domain is handled by mail.example.com. Now we must make sure that mail.example.com points to the same address as our server (atlantis.example.com).

  atlantis:~# nslookup mail.example.com
  Server:         YOUR-DNS-SERVER
  Address:        YOUR-DNS-ADDRESS#53

  Non-authoritative answer:
  mail.example.com        canonical name = example.com.
  Name:   diabmon.com
  Address: YOUR-IP-ADDRESS

It would be also nice if your reverse DNS points to the same name (atlantis.example.com)

  atlantis:~# nslookup YOUR-IP-ADDRESS
  Server:         YOUR-DNS-SERVER
  Address:        YOUR-DNS-SERVER#53
  
  Non-authoritative answer:
  YOUR-IP-ADDRES-REVERSE.in-addr.arpa      name = atlantis.example.com.

If they do not match. Ask your ISP to change this for you.