How to configure DNS for OpenSRS Hosted Email

This article will outline how to configure your DNS records to point to the OpenSRS Hosted Email servers.

Note: Do not make any DNS changes until the domains and mailboxes are set up on the OpenSRS Email Service system.

Types of DNS records

There are many types of records that the DNS system maintains. The important record types for the OpenSRS Email Service are MX and CNAME records.

Email Exchange (MX) records

The Email Exchange (MX) record is the line within the DNS zone file that directs email for a specific domain to the appropriate email server. It tells the rest of the world where a mailbox is located.

Zone file—A file on a root server that contains domain name registration information. Zone files contain information that is needed to resolve domain names to IP addresses and also contain all the information related to one domain. Zone files are also called master files.

MX—Short for mail exchange record, an entry in a domain name database that identifies the mail server that is responsible for handling emails for that domain.

When more than one MX record is entered for any single domain name that is using more than one mail server, the MX record can be prioritized with a preference number that indicates the order in which the mail servers should be used. This enables the use of primary and backup mail servers.

Canonical Name (CNAME) records

A Canonical Name (CNAME) record is a record in a DNS database that indicates the true or canonical host name of a computer. A computer hosting a Web site must have an IP address in order to be connected to the World Wide Web. The DNS resolves the computer’ domain name to its IP address, but sometimes more than one domain name resolves to the same IP address, and this is where the CNAME is useful. A machine can have an unlimited number of CNAME aliases, but a separate CNAME record must be in the database for each alias.

OpenSRS uses CNAME records to identify the OpenSRS POP, IMAP, and SMTP server. It allows users to access email at <yourdomain>.com instead of <yourdomain>.cust.<cluster.>.hostedemail.com, which is the active domain on the OpenSRS system.

Note: Do not use A records or IP addresses in place of CNAME hostnames. If an A record is used to identify the OpenSRS email server, email service will be disrupted if OpenSRS changes the IP address.

Example Mail DNS configurations

OpenSRS Email Service’s IP addresses include clusters represented by the variable <cluster> in the following examples.

Omission of the cluster from a DNS record will cause the default cluster, A, to be used.

Currently, OpenSRS Email employs two clusters: A and B.

Note: If you do not know what cluster you are on, please review this article.

Examples are provided for DNS configuration in both the Test and Live environments.

Test

There is only one test environment.

You can use this simple example to configure the required DNS records for your domain within the Test environment.

The example domain used is example.org. Replace example.org with <your_domain.tld>.

mail.example.org.	IN CNAME
   mail.example.org.cust.test.hostedemail.com.
example.org.		IN MX 0
   mx.example.org.cust.test.hostedemail.com.

Live

You can use this simple example to configure the required DNS records for your domain within the Live environment.

If you are creating email accounts on a root domain, such as admin@example.org, the DNS records are as follows (replace example.org with <your_domain.tld>): 

mail.example.org.		IN CNAME
   mail.example.org.cust.<cluster>.hostedemail.com.
example.org.		IN MX 0
   mx.example.org.cust.<cluster>.hostedemail.com.
If you are creating email accounts on a subdomain, such as admin@finance.example.org, the DNS records are as follows (replace example.org with <your_domain.tld>): 
finance.example.org.		IN CNAME
   mail.example.org.cust.<cluster>.hostedemail.com.
finance.example.org.		IN MX 0
   mx.example.org.cust.<cluster>.hostedemail.com.

Example Filter-only DNS configurations

Test

You can use this simple example to configure the required DNS records for your domain within the Test environment.

The example domain used is example.org. Replace example.org with <your_domain.tld>.

spam.example.org.		IN CNAME
   mail.example.org.cust.test.hostedemail.com.
example.org.		IN MX 0
   mx.example.org.cust.test.hostedemail.com.

In this example,

  • Web-based spam quarantine is at http://spam.example.org/,
  • the IMAP server is spam.example.org, and
  • the Email Exchange is at example.org.

Note: spam, portal and spamportal are all acceptable prefix components to your domain name.

Live

You can use this simple example to configure the required DNS records for your domain within the Live environment.

The example domain used is example.org. Replace example.org with <your_domain.tld>.

portal.example.org.		IN CNAME
   mail.example.org.cust.<cluster>.hostedemail.com.
example.org.			IN MX 0
   mx.example.org.cust.<cluster>.hostedemail.com.

In this example,

  • Web-based spam quarantine is at http://portal.example.org/,
  • the IMAP server is portal.example.org, and
  • the Email Exchange is at example.org.

Note: spam, portal and spamportal are all acceptable prefix components to your domain name.

White listing OpenSRS Email Service

If you want to ensure that filtered mail reaches your users, include our IPs from which we send the filtered mail in your white list.

As of June, 2016 the filtering IPs are:

Cluster A 216.40.44.0/24
  216.40.42.17/32
Cluster B 64.98.42.0/24
  64.98.36.17
Test 216.40.41.5/32
  216.40.41.17/32

Please check with OpenSRS Support if you need to troubleshoot or verify this information.

Have more questions? Submit a request

0 Comments

Please sign in to leave a comment.
Powered by Zendesk