What is a mail exchanger? Definition and importance for your email deliverability

A mail exchanger (MX) is a fundamental part of how emails get delivered to the right inbox. In other terms, it’s the server responsible for receiving emails on behalf of your domain. 

It means that if your MX records aren’t set up correctly, your emails might never reach their destination, hurting your deliverability and business communication. If you want to learn about what an MX is, why it’s essential, and especially how it directly affects your email deliverability, you’re at the right place. 

What is a mail exchanger?

A mail exchanger (MX) is a type of DNS record that directs email traffic for your domain to the correct mail server. In simple terms, it tells the internet where to send emails intended for your domain. 

Without proper MX records, your emails can’t be delivered, period. 

So they play a fundamental role in managing your email communications because they ensure that messages are routed to the right place, whether it’s your business email server or a third-party provider like Google Workspace. 

If your MX records are incorrect or missing, you’ll face serious email deliverability issues: emails won’t reach you, and your outbound emails might not be trusted either. 

So, understanding what a mail exchanger is and configuring it properly is non-negotiable for reliable email communication and maintaining a strong sender reputation.

How does a mail exchanger work?

A mail exchanger (MX) works by acting as the gateway for all incoming and outgoing emails for your domain. When someone sends an email to your domain, the MX record in your DNS settings tells the sender’s mail server where to deliver the email. 

In practice, it establishes an SMTP connection with the recipient's mail server to ensure the email is routed to the right place. The MX record is essential here, because it indicates which server is responsible for handling your mail delivery. 

Without this step, emails would have nowhere to go. The MX server then accepts the email on behalf of your domain, verifies the sender, and ensures that it meets security protocols. After that, it delivers the email to the intended mailbox, and the job is done. 

The role of DNS MX records in email delivery

DNS MX records are the backbone of your email delivery system. Why ? Simply because they tell the internet which mail server is authorized to receive emails on behalf of your domain. So when someone sends you an email, their mail server directly looks up your DNS MX record to find out where to deliver it. 

Literally, these records “point” to the mail server that should handle your incoming mail. If your MX records aren’t set up correctly, your emails can go missing, get rejected, or land in the wrong place. In short, without proper MX configuration, your email communication falls apart. 

So this is why correctly setting up your mail exchange MX records ensures that your emails are delivered to the right server, every time, keeping your business communication smooth and reliable.

Read also: How to check your domain reputation and improve it ?

What is the priority of MX records?

The priority of MX records determines the order in which mail servers receive emails for your domain. Each MX record has a numeric value called a priority number. The lower the number, the higher the priority. 

For example, if you have multiple MX records, the one with the lowest priority number is the primary server that receives your emails first. So if that server is unavailable, the next server with a higher priority number steps in to handle the mail.

The whole point of this system is to ensure that your email communication doesn’t break down if one server goes offline. This is why correctly configuring these priority numbers is absolutely critical for reliable email delivery, especially for businesses that can’t afford missed messages. 

Our conclusion: having multiple MX records with appropriate priority settings provides redundancy and keeps your email system running in the good way, no matter what.

The importance of mail exchangers for email deliverability

The importance of mail exchangers is huge: they are the mail servers responsible for receiving and routing your emails to the correct IP addresses. 

In practice, if your mail exchangers are properly configured, your emails will easily reach their destination, which will help you to maintain a good sender reputation. However, misconfiguration can lead to serious issues, because your emails might bounce back, get lost, or never leave the server at all. Why? Because incorrect MX records can signal to email providers that your domain isn’t trustworthy (meaning you have a bad domain reputation), leading to deliverability problems, even for outgoing messages. 

So for any business relying on email, especially in B2B, getting this right is non-negotiable.

Load balancing and failover using multiple MX records

If you have multiple MX records, it’s like having a backup plan for your email system. Each record points to a different mail server, and they’re arranged with priority numbers. So if one server can’t handle the load or goes down, the next one in line takes over. 

This is failover: it keeps your emails from getting stuck or lost when there’s a problem with the primary server.

Load balancing works in a similar way. You can prevent any single server from being overwhelmed by distributing incoming emails across several servers, which is especially useful if you’re dealing with a high volume of emails. It’s like spreading out the work so that no server is under too much pressure. The result? Your emails get delivered efficiently, even during peak times or if there’s a server issue. And that’s it.

Here, the main interest for business is that this setup means no downtime, fewer bounced emails, and a reliable email system that keeps working even when things go wrong. So yes, it’s a simple yet powerful way to ensure that your email communication stays solid, no matter what.

Common issues with mail exchangers and how to fix them

Misconfigured mail exchangers can seriously mess up your email delivery. Whether it’s incorrect DNS settings, wrong priority numbers, or server issues, these problems can really stop your emails from reaching the right inbox.

It means that if your MX records don’t point to the right mail servers, your emails might bounce back or disappear into the void. The good news? Most of these issues are fixable with a few targeted adjustments. Here’s a rundown of common problems and how to solve them:

Here are more details for your knowledge: 

• Incorrect DNS settings: If your MX records don’t point to the right servers, emails can’t be delivered. So log into your DNS management and ensure each MX record is pointing to the correct mail server.
• Wrong priority numbers: If you have multiple MX records with the same priority number or in the wrong order, the system can get confused. Assign unique priority numbers to each MX record. The lower the number, the higher the priority. Make sure your primary server has the lowest number.
• Server downtime: If your primary mail server goes down and there’s no backup server configured, you’ll lose emails. You need to set up multiple MX records with proper priorities so a secondary server can handle emails if the primary one fails.
• No MX record configured: Without an MX record, your domain can’t receive emails at all, so make sure to add an MX record in your DNS settings that directs emails to the right mail server.
• Reverse DNS lookup failures: Receiving servers use reverse DNS lookups to verify your server’s identity. If there’s a mismatch, your emails could be rejected, so be sure that your reverse DNS is set up correctly, matching your mail server’s IP to your domain.
• Authentication issues: Even with the correct MX settings, if your SPF, DKIM, or DMARC records aren’t set up right, your emails can still get marked as spam. Remember to check these records in your DNS settings and verify they’re configured properly to pass authentication.

FAQs about mail exchangers

What does mail exchange do?

A mail exchanger (MX) handles the delivery of emails for your domain. In simple terms, when someone sends an email to your domain, the mail exchanger directs the message to the correct mail server responsible for processing and delivering it to the recipient’s inbox. So it acts as a traffic controller, making sure that your emails are really reaching their destination without getting lost or bounced back!

What is a mail exchanger in NSlookup?

In NSlookup, a mail exchanger refers to the MX records that can be queried to see which mail servers are set to handle email for a particular domain. So by using NSlookup, you can check these MX records to verify that they point to the correct servers. Keep in mind that this is useful for troubleshooting email issues, as it allows you to identify potential problems affecting your email deliverability, such as incorrect DNS settings or missing records.

What is a mail exchanger in MX records?

A mail exchanger in MX records is the specified mail server that manages email delivery for your domain. MX records in DNS tell other servers where to send emails addressed to your domain. They include priority numbers, determining the order in which servers handle incoming mail. It means that without properly configured MX records, your domain can’t receive emails. At all. 

What is a local mail exchanger?

A local mail exchanger is a mail server that handles email delivery specifically for local recipients within the same domain or network. It’s different from other mail exchangers, which may handle both internal and external email traffic. Local mail exchangers are typically used in internal email systems to manage communications within an organization, without routing messages through external servers.