MX record priority and setup explained

Have you ever wondered how email messages know where to go? Behind the scenes, a crucial component called an MX record ensures that emails are routed properly to your domain’s mail server. If you’re managing a domain, understanding MX records—particularly their priority and setup—is essential. Misconfiguration can result in failed email delivery, exposing you or your organization to potential communication lapses.

What is an MX Record?

An MX (Mail Exchange) record is a type of DNS (Domain Name System) record that directs email to a mail server. When an email is sent to your domain, internet mail servers look up your domain’s MX records to determine where to deliver the message. These records tell the sender’s email server how and where to deliver the message.

Each MX record contains two primary components:

• Priority Value: A number that determines the order in which servers should be used. Lower numbers indicate higher priority.
• Mail Server Hostname: The domain name of the mail server that will handle the email (e.g., mail.example.com).

For example, a domain might have two MX records:

10 mail1.example.com
20 mail2.example.com

In this setup, emails will first try to go to mail1.example.com. If it is unavailable, they’ll be routed to mail2.example.com as a fallback. This structured system ensures both primary and backup delivery options.

Understanding MX Record Priority

The priority value associated with an MX record indicates the order in which the mail servers are tried. This priority number is interpreted in ascending order: the lower the number, the higher the priority.

Here’s how email routing works with multiple MX records:

1. The sending server queries the receiving domain’s DNS for MX records.
2. It gets a list of mail servers and their associated priorities.
3. The server then attempts to deliver the message to the mail server with the lowest priority number.
4. If that server is unavailable (due to downtime, network issues, etc.), the sending server will attempt delivery to the next higher number, and so on.

So, assigning proper priorities ensures load balancing and redundancy—critical for business continuity.

How to Set Up MX Records

Setting up MX records involves working with your domain’s DNS settings. You’ll typically access these settings in your hosting provider’s control panel or DNS management console (such as GoDaddy, Cloudflare, or AWS Route 53).

Steps to Set Up MX Records Properly

1. Log in to your DNS management console.
2. Navigate to the DNS settings for your domain.
3. Locate the MX section or add a new MX record if necessary.
4. Enter the mail server hostname (e.g., mail.example.com).
5. Assign a priority value (commonly 10, 20, 30, where 10 is the highest priority).
6. Repeat for any additional mail servers acting as backups.

Once the records are added, DNS propagation may take some time (up to 48 hours), during which mail routing stabilizes to the new configuration.

Common Configuration Example

Here’s a practical example of a standard MX configuration for a company using Google Workspace (formerly G Suite):

1    ASPMX.L.GOOGLE.COM
5    ALT1.ASPMX.L.GOOGLE.COM
5    ALT2.ASPMX.L.GOOGLE.COM
10   ALT3.ASPMX.L.GOOGLE.COM
10   ALT4.ASPMX.L.GOOGLE.COM

Notice how multiple servers have the same priority. This enables distribution of the load across those servers. If one fails, the another is automatically attempted.

Best Practices for MX Record Configuration

When managing email reliability and security, proper MX record configuration is a vital aspect. Here are some industry best practices to follow:

• Use Fully-Qualified Domain Names (FQDN): Avoid using IP addresses. DNS names are preferred because they’re easier to manage and more flexible.
• Have Backup MX Records: Ensure at least one secondary server is listed as a failover option.
• Don’t Set Too Many Records: While redundancy is good, avoid cluttering your setup with unnecessary entries. About 3–5 entries is typically sufficient.
• Keep Priorities Logical: Stick with standard values like 10, 20, 30 to make priorities clear and manageable.
• Check for Typos: An incorrect domain name or missing period can result in undelivered mail or improper routing.

Image not found in postmeta

Verifying Your MX Records

After setting your MX records, it’s crucial to confirm that they’ve been correctly applied. You can verify MX records using various tools:

• Command Line: Use nslookup -q=mx yourdomain.com or dig mx yourdomain.com.
• Online Tools: Websites like MXToolbox or DNS Checker can provide real-time MX record reports.

Verification confirms not only that your records have propagated, but also detects potential issues like duplicate entries or unreachable servers.

Troubleshooting MX Record Issues

Even slight misconfigurations can lead to major problems in email delivery. Here are some of the most common issues and their solutions:

• Emails Not Arriving: Confirm MX records are pointing to valid and functioning mail servers. Use DNS tools to verify.
• Wrong Priorities: If backup servers are receiving emails when they shouldn’t, check if your priorities are set correctly (lowest number = highest priority).
• Missing DNS Propagation: Changes to MX records take time. If your records aren’t working yet, check whether they’ve propagated across global DNS resolvers.
• Firewall or Port Blocks: Ensure your mail servers are reachable via the proper ports (typically TCP 25, 465, or 587).

Consistently monitor your mail delivery and use automated alerts or uptime monitoring for mission-critical systems.

MX Records and Email Security

While MX records manage email delivery, security protocols like SPF, DKIM, and DMARC play a role in preventing spoofing and phishing. Still, incorrect MX records can allow spammers to bypass protections if misrouted.

Always ensure your MX records are accompanied by strong email security configurations. This includes:

• SPF Records: Defining which mail servers are allowed to send messages on behalf of your domain.
• DKIM: Enables signing outgoing messages to verify authenticity.
• DMARC: Builds on SPF and DKIM to determine what to do with suspicious messages.

Remember: a secure mail system is only as reliable as its DNS configuration.

Conclusion

MX record configuration is a foundational requirement for any organization or individual relying on domain-based email communication. Understanding how MX priority works allows you to design a more robust, fail-safe, and scalable mail delivery system. Whether setting up email for a small business or managing an enterprise’s email infrastructure, the correct setup and ongoing maintenance of MX records ensures reliable communication, resilience in case of network failure, and even contributes to your domain’s email reputation.

Take the time to audit, monitor, and update your records periodically. Email is too important to leave to chance, and with the threats of cyberattacks and data loss, ensuring correct mail routing should be at the top of your IT priorities.