MX Explained

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MX Explained

MX (Mail Exchange) records allow mail servers to route emails to the right place. This includes bounce backs that often go untracked and unrecorded, skewing email marketing metrics.

When you send an email to Sam at, the message doesn’t go straight to Sam. The message gets sent to an outgoing mail server (SMTP), which is equivalent to a local post office that you would send a letter from. When this online post office receives an email, it doesn’t automatically know where to send it based on the address. Computers don’t talk in English, they communicate through IP addresses, so the IP address of the domain, needs to be looked up before the email can be delivered.

What is being looked up is the MX record which tells the ‘post office’ which mail servers receive email for that domain i.e. which post office to send it to. Without an MX record in place, a domain cannot receive emails.

MX Priority Servers

Email servers can fail and have outages, meaning they don’t work all of the time. You don’t want to lose connectivity to your email so you set up multiple servers that can receive mail to your domain. This way, when one server isn’t working, the system will attempt to deliver the email to others until it finds one that works. When MX is configured, these servers are added to the MX record and given a priority.

Bounce Backs

A common problem for organizations is that their domain’s MX record isn’t set up to properly route bounced mails. When this happens, bounced emails go unrecorded and the sender is never made aware of the fact that their message never reached its intended recipient.

That’s bad enough for one message but, for marketers sending out thousands of emails, it will severely skew their metrics. The industry standard sees approximately 20% of emails get bounced, that’s 1 in 5. When you send 100 emails, 20 bounce, but you don’t know this, so you measure open and click through rates against the 100 that were sent, not the 80 that got delivered.