Knowledge Base

Mail Exchange (MX) records are used by mail servers to determine where to deliver email for a domain. If your domain does not send or receive email directly, there is no reason to configure this record type. 

In order for an MX record to function properly, it must map to an external mail server or a domain by means of an A (or AAAA) record. Servers use levels or priority settings to resolve MX records, and in this case, the record with the lowest priority is the preferred destination for emails coming to and from your domain.

If an email is sent to a domain without an MX record, a mail server will attempt delivery via a corresponding A record. For instance, if the domain “anexampledomain.com” did not have any MX records configured, mail servers would attempt to deliver email to the IP address in the A record (if the A record exists).

Note: MX records should never point to a CNAME record.

Common Use Cases for MX Records

While MX records do not support DNS Failover, they can achieve a similar result when multiple MX records are configured for a domain. When you have alternative mail servers, you can set the MX Level (priority) for each server based on preference. This would be done in the MX Level field of the record, which instructs servers on which mail server should be used first, second, third, fourth, and so on.

For example, if you have a domain with three mail servers, and you configured your MX record to have one server at level 10, the second server at level 20, and the third at 30, resolvers would attempt to send mail to the server set to level 10. If the preferred server was unavailable, it would send an email to the server at level 20 and would continue down the list.

If you have multiple MX configurations with the same MX level, then servers will treat it as a round-robin configuration, and balance the load between each email server.

Note: MX Levels are commonly configured in increments of 5 or 10, but can also start at 0 and just be single digits, or even 53 or 102. Many people use increments of 5 or 10 for ease of use or to allow for future adjustments, but this also depends on your organization’s policies and preferences.

Prerequisites

• A domain is already added to your Constellix account
• You have all the necessary IP addresses or hostnames for your domain
• You have an A or AAAA record already configured for your domain

Note: Visit our tutorials on creating records if you need help with record creation. If you need help adding a domain, we have a guide that walks you through the process.

How to Create an MX Record in Constellix

1. Log into Constellix and Select Domain

Log into Constellix. Once in the dashboard, select your domain from the Recently Updated Domains list or search for the domain in the top-left search bar.
 

2. Expand MX Records

After selecting the domain that needs the MX record, you will be taken to the Records page.  If you have not configured any MX records for this domain yet, click the green + icon beside the MX record to expand options, otherwise skip to step 3.
 

3. Add MX Record

Once options are expanded, click the green + icon to create your MX record.
 

4. Enter Record Values and Save

You should now see the Add MX Record pop-up window.

Fill out the following values:
 

a) Name: Enter the FQDN/hostname for the record.

b) TTL: Time to live (measured in seconds) determines how long a record is cached in nameservers.

Visit our What is TTL resource for more information and best practices for TTLs.

Note: For records that do not change often, such as MX records, we recommend setting TTL values between 3600 (1 hour) to 86400 seconds (24 hours). If you are planning to update your MX records, lowering the TTL before making changes will help speed up propagation.

c) Disable Record: With this feature, you are able to remove records from our nameservers without removing the record configuration in the Constellix DNS control panel.

See our Disabling a Record tutorial for more information.

d) Server: Enter the destination mail server for the domain. If you point to a server outside of your managed domain, the email for “anexampledomain.com” will go to “mx.externalserver.com.”

e) Level: The MX level (priority) determines the order in which mail servers will attempt to deliver email for your domain. 

f) Notes: Add a helpful note with keywords so you can search for your records later (optional, but recommended).

g) Save: If you need to add an additional MX record, tap the green Save and Continue button, otherwise, click on Save and Close. 

Note: In order for your MX record to take effect, you must review and apply changes.

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