IMail Server 8.01 User's Guide - Checking the DNS Configuration for the Primary Host

Checking the DNS Configuration for the Primary Host

For background information about DNS records, see "Appendix A: Mail Servers and the DNS" in the IMail Server Getting Started Guide.

Setting Up DNS for the Primary Host

You need to verify or create the following entries for your primary mail host in your DNS:

An MX record for the mail domain (for example, domain.com). The MX record identifies the host name of the computer running the mail server (in this case, the IMail Server computer).
An A record for the host name of the computer running IMail Server. The A record maps a host name to an IP address.
A PTR record for the IP address of the computer running IMail Server. The PTR record maps an IP address to the host name and is used for reverse lookups.

As an example, the DNS entries for a host for which the official host name in IMail Server is mail.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 mail.domain.com.

Setting Up DNS for Multiple Mail Hosts

For a virtual host with an IP address, you need to make the following entries in your DNS:

An MX record for the mail domain (for example, mail.domain2.com). The MX record identifies the host name of the virtual host.
An A record for the host name of the virtual host. The A record maps a host name to an IP address.
A PTR record for the IP address of the virtual host. The PTR record maps an IP address to the host name and is used for reverse lookups.

As an example, the DNS entries for a virtual host for which the host name in IMail Server is mail.domain2.com would look like:
SOA 
$ORIGIN 
... 
domain2.com 
     IN MX 10 mail.domain2.com		(MX record) 
     mail IN A 156.21.50.10		(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@domain2.com would find that the mail must be sent to the host mail.domain2.com.

For a virtual host without an IP address, you need to make only one entry in your DNS: an MX record for the mail domain (for example, mail.domain3.com). This MX record identifies the host name of the primary mail host. As an example, the DNS entries for a virtual host without IP address for which the host name is mail.domain3.com would look like:
SOA 
$ORIGIN 
... 
domain3.com 
     IN MX 10 mail.domain.com  
A DNS lookup for mail sent to user@domain3.com would find that the mail needs to be sent to the host mail.domain.com.

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