Problem

What is Backup MX?

Solution:

backupMX (also known as SMTP Backup, Secondary SMTP, or Secondary Mail eXchanger) is a failover email service designed to protect email delivery when your primary mail server is unavailable. It works by temporarily accepting incoming email on your behalf if your main mail server goes offline, ensuring messages are not lost or rejected.

In a standard email setup, domains rely on a single MX (Mail Exchange) record that points to one mail server. If that server becomes unreachable due to maintenance, network issues, or unexpected outages, incoming email may fail. A Backup MX provides an additional layer of resilience by acting as a secondary destination for incoming mail.

Why Having a Second MX Record Is Important

Email is a critical business service, and even short periods of downtime can result in missed messages, failed deliveries, or reputational damage. By configuring a second MX record that points to a Backup MX server, you significantly improve your email reliability.

The benefits of a secondary MX record include:

• Improved email continuity - messages are still accepted even if your primary server is offline
• Protection against outages - covers maintenance windows, hardware failures, or network problems
• No lost emails - messages are queued securely until delivery is possible
• Business continuity - customers, partners, and staff can continue emailing without interruption

Without a Backup MX, sending servers may retry delivery for a limited time before bouncing messages back to the sender, which can result in lost communication.

How Backup MX Works

BackupMX works by using MX record priority in your domain’s DNS settings. Each MX record has a priority value, lower numbers are tried first, meaning the lower the number the higher the priority.

Here’s how the process works in practice:

1. Normal operation - Incoming email is delivered to your primary mail server (lowest MX priority number).
   
   
2. Primary server offline - If the sending mail server cannot connect to your primary MX, it automatically tries the next available MX record (The next higher MX priority number). In this case a backupMX server.
   
   
3. Temporary message storage - The BackupMX server accepts and securely stores (queues) incoming emails instead of rejecting them.
   
   
4. Automatic redelivery - Once your primary mail server comes back online, the BackupMX automatically forwards the queued emails for final delivery to the primary mail server.

This process is fully automatic and requires no action from the sender or recipient.

Who Should Use BackupMX?

BackupMX is particularly useful for:

• Businesses running on-premise mail servers
• Organisations with strict uptime requirements
• Companies that cannot afford missed or bounced emails
• Domains with single-server email configurations
• Any organisation seeking better email resilience and reliability
• Companies needing a service to accept emails when doing maintenance on the primary server, or primary server migration.

Even cloud-based email systems can benefit from Backup MX (backup SMTP) as an additional safeguard against outages or configuration issues.

Backup MX as Part of a Resilient Email Strategy

BackupMX should be viewed as part of a broader email resilience strategy, alongside proper DNS configuration, monitoring, and spam protection. When implemented correctly, it provides peace of mind that incoming email will always be accepted; even when your primary infrastructure experiences problems.