If someone emails you and gets a bounce-back, at least they know to try another way. But what if the email simply vanishes — no delivery, no error, the sender thinks it went through, and you never receive it?

That is what happens when your MX records are missing or misconfigured. It is more common than most businesses realise, and the costs can be significant.

What Are MX Records?

MX stands for Mail Exchange. MX records are DNS entries that tell the internet which mail servers accept email for your domain. When someone sends an email to [email protected], their email provider looks up the MX records for yourcompany.co.uk to find out where to deliver it.

Without MX records — or with records pointing to non-existent or incorrectly configured servers — incoming emails have nowhere to go. Depending on the sending server’s configuration, the email might bounce back, silently fail, or queue until it times out days later. Often, the sender receives no error at all.

What Happens When MX Records Go Wrong?

Missed sales enquiries. A potential customer sends a direct email. It never arrives. They do not chase — they find a competitor instead.

Missed supplier communications. An invoice, a contract, a delivery notice — any of these arriving during an MX outage can cause real operational disruption.

Authentication failures. Correct DNS configuration underpins email security standards including SPF, DKIM, and DMARC. Broken MX records can indicate broader DNS issues that affect the trust your domain’s email enjoys.

Account recovery lockout. If you use your domain email for cloud services, banking, or software licences, broken email delivery can lock you out of critical accounts when you need to reset passwords.

The Security Risk of Abandoned Domains

This is the most overlooked MX risk. When businesses migrate to new domains or rebrand, old domains are sometimes left with MX records pointing at email services that have since been cancelled.

Security researchers have repeatedly demonstrated that organisations leave behind old domains that still receive sensitive email. In 2023, researchers found they could register lapsed domains that large companies had once used and immediately begin receiving emails including login links, internal forwards, and supplier communications — simply because MX records still pointed at infrastructure that had since expired.

For small businesses, the risk is that email services are cancelled without updating or removing associated DNS records. Anyone who registers the old mail service namespace — or in some cases the domain itself — can then intercept your email.

Downtime During DNS Changes

Temporary MX failures are also a genuine risk. If you change hosting provider, move email platforms, or modify DNS without care, your MX records can point to nothing for hours or days while DNS changes propagate.

DNS TTL (Time To Live) settings determine how long old records are cached. If your TTL is set to 24 hours, a misconfiguration can take a full day to propagate even after you fix it — meaning a full day of lost email. A reasonable TTL for MX records is between one and four hours.

What to Do Next

  • Check your MX records now. Use any DNS lookup tool or W3IT’s free security check. Confirm the records point to your actual, active mail provider.
  • Remove any old MX records. If you have switched email providers, delete records pointing to the old platform. Leaving them creates both delivery confusion and a potential security vulnerability.
  • Check your TTL. Very long TTLs (24 hours or more) slow your ability to recover from misconfiguration.
  • Monitor for unexpected changes. DNS changes can be made by anyone with access to your registrar account. Unexpected changes to MX records are a potential indicator of domain hijacking.
  • Do not forget parked or old domains. If you own other domains — old business names, common misspellings, previous brands — check their MX records. Either configure them properly or remove the records entirely.

Getting MX records right is basic housekeeping, but it is surprising how often businesses discover problems only when something important goes missing.

W3IT’s free security check checks your MX records as part of a comprehensive review of your domain’s DNS and security configuration. It takes seconds — run it now before you find out the hard way that an email you needed never arrived.