MX Record Lookup

What Are MX Records?

MX (Mail Exchanger) records are DNS records that direct email to the correct mail servers for a domain. When someone sends an email to user@yourdomain.com, the sending mail server performs an MX lookup to discover which servers accept email for yourdomain.com.

Each MX record contains two key pieces of information: a priority number and a mail server hostname. The priority determines which server is tried first — lower numbers have higher priority. If the primary server is unavailable, the sending server automatically tries the next-priority MX record, providing built-in redundancy for email delivery.

How MX Records Work

The email delivery process using MX records follows these steps:

1. Sender's mail server extracts the domain from the recipient address (e.g., yourdomain.com from user@yourdomain.com)
2. Performs a DNS query for MX records: dig yourdomain.com MX
3. Receives a list of mail servers sorted by priority
4. Attempts to connect to the lowest-priority (highest-preference) server via SMTP (port 25)
5. If that server is unavailable, tries the next priority level
6. Delivers the email to the first responding server

Understanding MX Priority

MX priority (also called “preference”) determines the order in which mail servers are contacted. Lower numbers = higher priority. This is a common source of confusion — priority 10 is preferred over priority 20.

Common priority conventions:

• Priority 1–10: Primary mail servers (tried first)
• Priority 20–30: Secondary/backup mail servers
• Priority 50+: Tertiary failover servers

When multiple MX records share the same priority, sending servers typically distribute email between them using round-robin — this provides load balancing. For example, Google Workspace uses two MX records with priority 5 for load distribution.

MX Records for Popular Email Providers

Google Workspace

Priority 1  → aspmx.l.google.com
Priority 5  → alt1.aspmx.l.google.com
Priority 5  → alt2.aspmx.l.google.com
Priority 10 → alt3.aspmx.l.google.com
Priority 10 → alt4.aspmx.l.google.com

Microsoft 365

Priority 0  → yourdomain-com.mail.protection.outlook.com

Zoho Mail

Priority 10 → mx.zoho.com
Priority 20 → mx2.zoho.com
Priority 50 → mx3.zoho.com

Fastmail

Priority 10 → in1-smtp.messagingengine.com
Priority 20 → in2-smtp.messagingengine.com

Common MX Record Issues

No MX Records

Without MX records, your domain cannot reliably receive email. While RFC 5321 allows fallback to the A record, most modern mail servers require explicit MX records. Use our lookup tool to verify your records exist.

Only One MX Record

A single MX record means a single point of failure. If that mail server goes down, all incoming email will queue on the sender's side (most servers retry for up to 5 days). Add at least one backup MX record for redundancy.

Incorrect Priority Ordering

If your backup MX has a lower priority number than your primary, email will be delivered to the backup first. Remember: lower number = higher priority. The primary mail server should have the lowest priority value.

Stale MX Records After Migration

After migrating email providers, old MX records may remain in DNS. This causes email to be delivered to the old provider, where the mailbox no longer exists. Always update MX records promptly during migration and verify with our lookup tool.

MX Records and Email Security

MX records are part of the broader email infrastructure that includes security configurations:

• MX Records — Direct email to the right servers (this tool)
• SPF Records — Authorize which servers can send email for your domain
• DKIM Records — Verify email integrity with cryptographic signatures
• DMARC Records — Define policies for emails that fail authentication

Together, these DNS records form the foundation of email delivery and security. Use our complete suite of email tools to verify your entire configuration.

Monitoring MX Records and Mail Servers

MX records pointing to the right servers is only half the equation — those servers need to actually be running. Silent MX failures mean email queues up on the sender's side for hours or days before anyone notices.

API Status Check can monitor your mail servers continuously — checking SMTP connectivity, response times, and DNS record consistency. Get alerted within seconds when a mail server goes down, before the email backlog becomes a problem.

Frequently Asked Questions About MX Records

What is an MX record?

An MX (Mail Exchanger) record is a DNS record that specifies which mail servers receive email for a domain. Each record has a priority number (lower = preferred) and a mail server hostname.

How do I check MX records?

Enter a domain in the MX lookup tool above and click “Lookup MX Records.” The tool queries DNS, displays records sorted by priority, and identifies the email provider.

What does MX record priority mean?

Priority determines which mail server is tried first. Lower numbers = higher priority. If the primary server (priority 10) is down, email routes to the next server (priority 20).

What happens if there are no MX records?

Without MX records, the domain cannot reliably receive email. Sending servers may attempt the A record as fallback, but this is unreliable. Always configure explicit MX records for email-receiving domains.

How do I find a domain's email provider?

Look up the MX records — the hostnames reveal the provider. Google Workspace uses aspmx.l.google.com, Microsoft 365 uses *.mail.protection.outlook.com. Our tool auto-identifies providers.

Can I have multiple MX records?

Yes, and it's recommended. Multiple MX records with different priorities provide failover redundancy. Most email providers configure multiple records by default.

How long do MX record changes take to propagate?

MX record changes propagate within minutes to hours, depending on the TTL value. During migration, keep both old and new MX records active to prevent lost email.

What is the difference between MX and A records?

MX records route email to mail servers. A records map domain names to IP addresses for web traffic and general hostname resolution. Both are DNS records serving different purposes.