What Is a Backup MX (Secondary MX) and Do You Need It?

If your mail server is briefly unreachable, what happens to incoming email? Usually it's held by the sender and retried - but a backup MX adds a safety net. Here's what it is and whether it's worth setting up.

A quick recap on MX records

MX (Mail Exchange) records tell the internet which servers receive mail for your domain, each with a priority number - lower numbers are tried first. See what are MX records.

What is a backup (secondary) MX?

A backup MX is an additional mail server listed with a higher priority number (so it's used second). If your primary mail server can't be reached, sending servers try the backup, which accepts the mail and holds it, then delivers it to your primary once it's back online.

Think of it as a receptionist next door who takes your post when your office is briefly closed.

Do you actually need one?

Here's the part many people don't realise: email already has built-in resilience. If no mail server is reachable, well-behaved sending servers queue the message and retry for days before giving up. So a short outage rarely loses mail even without a backup MX.

A backup MX mainly helps when:

• You want incoming mail accepted instantly during an outage rather than queued at the sender
• You run your own mail infrastructure with meaningful downtime risk

The downsides

• Spam risk - backup MX servers are a classic target for spammers, and a poorly configured one can become a spam relay or let more junk through
• Complexity - another server to maintain and keep in sync
• Often unnecessary - with a reliable, highly-available email host, the primary rarely goes down long enough to matter

The modern answer: reliable hosting beats backup MX

For most businesses, the better investment isn't a backup MX - it's an email host with high availability and strong uptime so the primary simply doesn't go down. Combined with the internet's built-in retry behaviour, your mail is safe without the extra moving parts.

Reliability built in

DigiCloudMail runs on globally distributed, highly available infrastructure with 99.99% uptime - so your primary mail is dependable, and incoming email keeps flowing without needing you to bolt on a backup MX. For the bigger picture on protection, see daily backups and recovery.

Want email that's reliable by design? Get in touch.