Setting Up DNS for the Primary Mail Host

To properly send and receive email, add the following records to your DNS server. If an Internet Service Provider (ISP) is hosting your DNS server, contact your ISP to have the appropriate records added to the DNS server.

MX Records. Create a Mail eXchanger (MX) record to identify the host name of the computer running the mail server. If you plan to host multiple domains, you need an MX record for each domain. The MX record points to the (fully qualified) host name of the IMail Server (the Primary Host). For example: domain.com IN MX 10 mail.domain.com
A Records. Create an Address (A) record for the IMail Server that has the IP address of the IMail Server (the Primary Host). The A record maps a host name to an IP address. For example: mail.domain.com IN A 156.21.50.15
PTR Records. Create an A pointer (PTR) record for reverse lookups. You need a PTR record that resolves the IP address of your IMail Server (the Primary Host) to the Official Host Name of your IMail domain. For example:
156.21.50.15 in-addr.arpa. host=mail.domain.com.
SPF Records (optional, but required for receiving mail servers to use SPF features). SPF records let other email services use SPF filtering (if the feature is available on the mail server) to protect against incoming email from forged (spoofed) email addresses that may be associated with your mail server. As SPF records are implemented more widely, SPF filtering will become more effective at identifying spoofed email messages. For more information, see the IMail Administrator Help or go to the SPF community at http://www.openspf.org/Project_Overview.

Example: The DNS entries for a host with an official host name of imailbox.domain.com would look like:

SOA $ORIGIN ... domain.com IN MX 10 mail.domain.com(MX record)mail IN A 156.21.50.5(A record)
5.50.21.156.in-addr.arpa.,type = PTR host = mail.domain.com(PTR record)

A DNS lookup for mail sent to user@domain.com would find that the mail must be sent to the host at mail.domain.com.