What Is an MX Record? Email Delivery Explained
An MX record is the DNS entry that tells the world which server accepts email for a domain. Here is how it routes mail, what priority values mean, and how to check yours.
Every email you send has to find its way to a specific server before it reaches an inbox. The thing that makes that possible is a small DNS entry called an MX record. If a domain has no MX record, or the wrong one, mail bounces or vanishes, and no amount of clever subject lines will fix it. Here is what an MX record actually does and how to read one yourself.
What an MX record is
MX stands for Mail Exchange. It is a type of DNS record that tells the rest of the internet which server is allowed to accept email for a domain. When someone sends a message to [email protected], their mail server does not magically know where to deliver it. It asks the DNS system one question: "Which server handles mail for example.com?" The answer comes back as one or more MX records.
Think of the domain as a street name and the MX record as the specific building on that street where post is collected. The A record (the one that points your website at a server) and the MX record are separate jobs. Your site can live on one host while your mail lives on Google Workspace, Microsoft 365, or your own mail server. The MX record is what keeps those two from getting confused.
How an MX record routes mail
Here is the sequence, start to finish, when a message leaves a sender:
- The sending server reads the recipient address and pulls out the domain (the part after the @).
- It queries DNS for the MX records of that domain.
- DNS returns a list of mail server hostnames, each with a priority number.
- The sender looks up the IP address of the chosen mail server (its A or AAAA record).
- It opens an SMTP connection and tries to hand over the message.
Priority values: lower means first
This is the part that trips people up. Each MX record carries a priority (sometimes called preference). It is a number, and the rule is counterintuitive: the lowest number is tried first. A record with priority 10 is preferred over one with priority 20. Lower equals more important.
A domain can list several mail servers so that if the main one is down, mail still has somewhere to go. A typical setup looks like this:
| Priority | Mail server | Role |
|---|---|---|
| 10 | mx1.example.com | Primary, handles everything normally |
| 20 | mx2.example.com | Backup, used only if mx1 is unreachable |
| 30 | mx3.example.com | Second backup |
If two records share the same priority, sending servers spread traffic across them roughly evenly, which is a simple way to load balance. Most managed providers handle all of this for you. Google Workspace, for example, gives you a single entry pointing at smtp.google.com, and that one host fans out behind the scenes.
How to check a domain's MX records
You do not need special software. A few quick options:
- Command line (Linux or macOS): run dig example.com MX +short. You get back the priority and hostname for each record.
- Windows: run nslookup -type=mx example.com in Command Prompt or PowerShell.
- Browser tools: MXToolbox and Google's Dig tool let you type a domain and read the records without touching a terminal.
When you read the output, check three things. Are there any MX records at all? Do the hostnames point at the provider you expect? And do the priorities make sense, with the primary on the lowest number? A domain with no MX record at all cannot receive mail through the normal path, which is a strong sign the address is dead.
Why this matters for sending and verification
MX records are the first real signal of whether an address can receive anything. A serious free email verifier starts by resolving the domain's MX records before it goes any further. No MX record means there is nowhere to deliver, so the address fails fast. If the MX records do exist, the verifier can connect to that exact server and check the mailbox, which is how Prime Verifier confirms Microsoft 365 and Google addresses without sending a real message.
If you send marketing or transactional mail, healthy MX lookups on your recipients are part of keeping bounces low. Pairing an MX check with good email list hygiene is one of the cheapest ways to reduce your bounce rate before a campaign ever goes out. For the wider picture, the complete guide to email verification walks through every step that sits on top of the MX lookup.
FAQ
Can a domain have more than one MX record?
Yes, and most do. Multiple records with different priorities give mail somewhere to go if the primary server is offline. Records with the same priority share the load. One MX record is fine too, especially with a managed provider.
What happens if a domain has no MX record?
By the old fallback rule, some senders would try the domain's A record instead, but most modern mail systems no longer do this reliably. In practice, no MX record usually means the domain cannot receive email, and any address on it is almost certainly undeliverable.
Does the MX record affect whether my mail lands in spam?
The MX record decides where mail goes, not whether it is trusted. Inbox placement depends on SPF, DKIM, DMARC, sending reputation, and content. If you want fewer messages in the spam folder, see how to improve email deliverability.