If you’ve ever wondered how an email travels from one address to another and ends up in your inbox, the answer involves something called an MX record. While it lives in the Domain Name System (DNS), its role is all about email: MX records point messages to the right servers so they actually arrive where they’re supposed to.
Let’s explore the role MX records play in keeping email moving smoothly and what that means for anyone working with domains that use email services.
What exactly is an MX record?
MX stands for Mail Exchanger. An MX record is a type of DNS (Domain Name System) record that tells email services where to deliver messages for a specific domain. Think of it as a digital address card; when someone sends an email to a domain, the MX record makes sure it gets delivered to the correct email service, just like a mailing address makes sure a letter ends up at the correct house.
For example, let’s say someone sends an email to [email protected]. Before that message can be delivered, the sending email server checks the domain’s DNS to ask, “Where should I send this?” The MX record provides the answer, pointing it to the mail server that handles email for that domain.
Because reliability is so important, most domains that handle email rely on more than one MX record. To make sure messages know which server to try first, each MX record has a priority number attached—the lower the number, the higher the priority. For instance:
- A domain may list several MX records, often pointing to different mail servers.
- An MX record with priority 10 will be used before one with 20.
- If the highest-priority server is unavailable, the sending mail server automatically tries the next MX record in line.
This redundancy ensures email delivery remains reliable, so that even if one server goes down, the domain can still accept email through another mail server listing in its MX records.
In other words, if your domain’s highest-priority mail server fails, the next one in line takes over so email delivery isn’t interrupted. This gives your domain a backup plan to help ensure emails still get through, even if something temporarily goes wrong.
How MX records are assigned during setup
When you set up email for a domain, your chosen email provider issues a set of MX records to use. Depending on the provider’s infrastructure, this might be just one record or as many as five, each with specific server addresses and priority values that tell sending mail servers where to deliver the domain’s email. For example, if you use OpenSRS Email, we’d provide you with MX records that point to our mail servers. If you set up your email on Google Workspace or Microsoft 365, you’d use their MX records.
To complete the setup, domain owners (or their service providers) log in to their DNS hosting providers and manually add or update the MX records in the domain’s DNS settings. If your or your clients’ domains use OpenSRS for DNS management—which is free for all domains registered through us—you can add your MX records through your OpenSRS account.
Why MX records matter
MX records are critical to making sure email gets delivered reliably. If they’re missing, misconfigured, or outdated, messages can get delayed, rejected, or vanish altogether.
In theory, a sender’s mail server might fall back to a domain’s A or AAAA record—the DNS entries that usually point to web servers. But since those aren’t designed for handling mail, depending on them is unreliable.
It’s like sending a letter to a company’s street address without naming the mailroom or recipient—it might find its way, but you can’t count on it.
To keep things running smoothly, it’s smart to:
- Use multiple MX records with different priority levels.
- Keep them accurate and up-to-date.
- Make sure they point to working, properly configured mail servers.
This kind of setup, where a domain uses multiple MX records, helps email systems stay reliable, especially when dealing with high volumes of messages or users. For example, an e-commerce company processing thousands of customer orders a day, or an SaaS platform supporting thousands of employee inboxes, can’t afford downtime. Multiple MX records give them the resilience to keep mail flowing even if one server goes down.
Best practices for MX record setup and email security
Whether you’re managing a domain’s DNS at OpenSRS or elsewhere, keeping these principles in mind will help you achieve stable, secure email performance.
1. MX records point to hostnames, not IP addresses
Instead of using a number like 192.0.2.1, MX records should point to a hostname, like mail.example.com. That hostname should already be set up with A or AAAA records that point to the mail server’s IP address—either by the email provider (like Google or Microsoft) or by whoever manages the mail hosting.
- An A record points to an IPv4 address (the most common type, like 192.0.2.1).
- An AAAA record points to an IPv6 address (newer format, like 2001:db8::1).
Using hostnames instead of hard-coded addresses makes management easier and more flexible. If an email provider changes the IPs behind their mail servers, the MX record doesn’t need updating—only the A or AAAA record tied to the hostname does.
2. Set a TTL (Time to Live) that matches service requirements
Every DNS record, including MX records, has a TTL. This value tells DNS resolvers (the systems that look up DNS records) how long they’re allowed to cache the record’s details before checking back for updates.
Why does this matter? Because DNS lookups happen constantly, caching helps speed things up and reduces unnecessary server load. But during setup, changes, or migrations, you want the system to check back more frequently in case something changes.
- During changes or migrations, use a lower TTL, like 36,000 seconds (1 hour), to ensure updates propagate quickly.
- Once everything is stable, you can raise it to a higher TTL, like 86,400 seconds (24 hours), to reduce DNS traffic and improve performance.
This approach helps balance speed during setup with efficiency in production.
3. Implement SPF, DKIM, and DMARC for authentication
These are additional DNS records that help protect your domain from spam, spoofing, and unauthorized email use.
- SPF (Sender Policy Framework): These tell email services which servers are authorized to send emails on your behalf, helping reduce the risk of spoofed messages that appear to come from your domain.
- DKIM (DomainKeys Identified Mail): These add a special signature to your emails to prove they’re real, helping prevent spoofing and phishing. They show that an email was sent from the right mail server and that the content hasn’t been tampered with.
- DMARC (Domain-based Message Authentication, Reporting, and Conformance): This is a method of authenticating emails. It tells email systems what to do if an email fails the SPF and DKIM checks. You can set it to block fake emails or mark them as spam.
Together, these records help build trust and reduce the risk of a domain being exploited by spammers or scammers.
4. Maintain security for backup MX records
Backup mail servers can be essential for maintaining email continuity, but they also pose a risk if not properly secured. In some cases, spammers specifically target backup servers because they’re overlooked or less protected.
To reduce this risk, backup servers should:
- Require authentication for message handling.
- Be regularly patched and monitored, just like primary mail servers.
- Avoid being left open to accept mail from any source. In practice, this means ensuring backup servers only handle mail for your domain and apply the same filtering as your primary servers.
OpenSRS gives you the tools to follow DNS and email best practices, making it straightforward to configure MX records and set up SPF, DKIM, and DMARC securely. While these records aren’t applied automatically, our platform provides a streamlined way to manage them.
Final thoughts
Email continues to be a vital part of online communication, and MX records are the behind-the-scenes tools that keep messages flowing to the right place. Keeping these principles in mind helps service providers recognize common pitfalls and see how reliable email delivery is maintained.
At OpenSRS, we make it easy to manage email at any scale, with tools that support automation, branding, and built-in DNS configuration. Whether you’re looking for a fully integrated platform or a more hands-on approach, we provide flexible options to match your business model:
For resellers and service providers who need scale and automation: The OpenSRS Email API lets you integrate provisioning, storage management, MX record setup, and password resets directly into your own systems. When domains are on OpenSRS nameservers, MX records are provisioned automatically—streamlining mailbox creation. For domains managed on another DNS provider, the API provides the necessary MX records so they can be added manually in the client’s DNS manager. With branding options, multilingual webmail, and built-in spam and virus filtering, you can deliver a seamless email experience that grows alongside your platform.
For agencies, designers, and IT consultants managing clients directly: The Reseller Control Panel (RCP) and Mail Administration Console (MAC) make it easy to deliver professional, hosted email services without the overhead of custom development. The same MX record provisioning applies here: automatic when using OpenSRS nameservers, and manual entry if the domains are on other DNS providers. Either way, mailboxes are ready as soon as DNS propagation completes, allowing you to offer clients a reliable, professional email solution without added overhead.
No matter your approach, OpenSRS gives you the infrastructure and support to offer reliable, secure, and easy-to-manage email hosting under your own brand.
Ready to get started? Explore our Hosted Email solutions and find the path that best fits your business.