What Is a DNS MX Record? A Simple Explanation
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Reading Time: 6 min
Key Takeaways
- A DNS MX record is essential for routing emails to the correct mail exchange server for a domain.
- Setting up MX records allows domain owners to control how messages are delivered across multiple domains.
- Priority numbers in MX records determine the order in which mail servers are contacted when sending emails.
- Using third-party email services typically requires configuring multiple MX records for both sending and receiving mail.
- Regularly checking your DNS MX records is vital for maintaining your domain’s email performance and health.
Email may feel instant, but in reality, a lot happens behind the scenes to ensure every message ends up in the right inbox. One of the key pieces that makes this possible is the MX (Mail Exchange) record. Think of it as a set of instructions that tells the internet where email for your domain should be delivered. More specifically, a DNS MX record is a type of DNS record that stores the mail exchange server for a domain.
Throughout this article, we will explain how MX records work, why they are essential for reliable email, and what to do if something goes wrong. By the end, you will have a clear understanding of how to set them up correctly and how to keep your email running smoothly.
What Is a DNS MX Record?
A DNS MX record is a type of record in the DNS that tells the Internet which mail server is responsible for handling email for a domain. In simple terms, it acts like an address label that directs email traffic to the right destination.
When someone sends you an email, their mail server looks up the MX record for your domain. That record points to the server that should receive the message. Without MX records, there would be no clear path for email delivery, and messages would not know where to go.
In the broader DNS system, MX records work alongside other records (such as A records and CNAME records) to make sure domain-related services, including email, function correctly.
Why do you need to configure DNS MX Records?
MX stands for Mail eXchanger, and it’s an essential part of how email works. It’s a record that’s set up by the owner of a domain to tell other servers where they can send emails for that domain. The MX record is usually tied to an A record, which tells you where you can find the server that hosts your domain.
When you set up an MX record, you tell other mail servers which server(s) you want them to use when they try to send emails for your domain. A DNS server will check that record before sending the message, so it knows where to send it if it can’t connect directly.
This is useful because it helps prevent spam from being sent from your domain and allows you to manage how messages are delivered from multiple domains without having to manage each one individually.
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If you’re using a third-party service like Google Apps, or Office 365, it’s likely they’ll provide you with two MX records: one for sending mail and one for receiving mail. The receiving MX should point to their servers, while the sending MX should point to your own server.
If you don’t have any third-party services, you might only need one MX record that points to your own server.
Common MX Record Components
MX records may look simple at first glance, but each part of the record plays an important role in how email gets delivered. Understanding these components will make it easier to set up your own records and troubleshoot issues if something goes wrong.
These components include:
- Priority value: The priority value tells the sending mail server which destination to try first. A lower number means higher priority. For example, if your domain has two MX records with priorities of 10 and 20, mail will attempt delivery to the server with priority 10 first. If that server is unavailable, the server with priority 20 will be used as a backup. This system provides reliability and ensures that email has multiple delivery paths.
- Mail server hostname: Each MX record must point to a mail server, written as a fully qualified domain name (FQDN), such as mail.example.com. Behind the scenes, this hostname is tied to an IP address that can accept incoming email traffic. The hostname is critical because it directs email to the right server, and usually reflects the service provider or system that manages your email.
- TTL (Time to Live) value: TTL defines how long the MX record information should be cached by other servers before checking again for updates. A shorter TTL is useful when you are making changes, since updates spread more quickly across the internet. A longer TTL reduces the frequency of lookups and can improve efficiency, but it also means changes take longer to apply.
Together, these three elements work as instructions that guide email reliably to its destination.
MX Record Examples
Given below is an example of an MX Record
| Domain Name | TTL | Class | Type | Priority | Hostname / Value |
| domain.com | 1800 | IN | MX | 10 | mail1.domain.com |
| domain.com | 1800 | IN | MX | 20 | mail2.domain.com |
Note: An MX record cannot point to a CNAME record which is a canonical name record used to setup domain aliases.
MX Preferences and Priorities
When you send an email, your computer contacts a mail server somewhere and asks it to deliver the message. The mail server has all the information about where to send the message. It looks at the destination address (the To: field) and finds the best server to deliver it.
But if you have more than one mail server for your domain, how does your computer know which one to use?
It uses a priority order. Mail servers that have higher priorities are contacted before those with lower priorities. If there are two servers with equal priority, the one with the lowest numerical value is contacted first.
The priority order is determined by your DNS records (MX records). The lower number is given higher priority. So if you have several mail servers set up with different priorities, they will be contacted in order from lowest number to highest number.
How are MX Records queried in the DNS?
DNS queries are a fundamental part of how the internet works. When you type in a URL in your browser, your computer makes a request for the IP address of that website to the DNS server on your internet service provider (ISP).
MX records are one type of DNS record used to look up where an email server is located. Just like any other type of DNS record, MX records are queried through DNS servers. The difference is that instead of looking up domain names like “google.com” or “nytimes.com,” you’re searching for their associated email server addresses instead.
When an email is sent to a recipient’s email server, the receiving MTA queries the sender’s DNS to verify the mail exchange servers responsible for sending the email. This is done by looking up the information published in the sender’s DNS MX records.
How to lookup and check your DNS MX Records?
When you are the domain owner, it is recommended that you closely monitor your DNS records to maintain your domain’s health and email performance. To do so, frequent DNS lookups and checks should be an integral part of your work cycle at regular intervals.
To check your DNS MX records, you can use our MX record lookup tool to perform a free and instant lookup on your MX records to reveal any underlying syntax or configuration error that may exist so that you can start troubleshooting.
Conclusion
MX records are a fundamental element of the Domain Name System, directing email traffic to the appropriate servers and ensuring reliable delivery. Correctly configured MX records prevent disruptions, reduce the risk of lost messages, and maintain the integrity of your domain’s email infrastructure.
Regular monitoring and management of MX records are essential to maintain consistent email performance, accommodate changes in mail servers, and safeguard communication. In short, well-maintained MX records keep your email running smoothly and ensure your messages reach their intended recipients without interruption.
Frequently Asked Questions (FAQs)
How many MX records can a domain have?
A domain can have multiple MX records to provide redundancy.
What happens if there are no MX records?
Without MX records, email delivery may fail or default to the domain’s main IP address, which is unreliable.
Do MX records affect outgoing emails?
No, MX records only control incoming email. Outgoing email is handled by your SMTP server.
Domain & Email Security Expert at PowerDMARC
Ahona is the Marketing Manager at PowerDMARC, with 5+ years of experience in writing about cybersecurity topics, specializing in domain and email security. Ahona holds a post-graduation degree in Journalism and Communications, solidifying her career in the security sector since 2019.
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