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§ T-08  —  Tool← All tools

MX record
checker

Look up the mail exchange records for any domain. See mail server priority, check for redundancy, and diagnose email delivery problems.

MX record lookup

Enter the domain without http:// or www.

§ 01MX records explained

How email finds its destination.

MX records are the address book of email routing — without them, no one can send you mail.

Step 01

Sender looks up MX

When someone sends to you@domain.com, their mail server queries DNS for the MX records of domain.com. The priority numbers tell it which server to try first.

Step 02

Connection to port 25

The sending server opens an SMTP connection to port 25 on your mail server's hostname. If the connection fails, it tries the next MX in priority order.

Step 03

Authentication checks

Your mail server runs SPF, DKIM, and DMARC checks on the incoming message. Failures may cause the message to be filtered or rejected depending on your policy.

Email that reaches the inbox.

Plunk handles SPF, DKIM, and DMARC setup and keeps your sending reputation clean so email lands in the inbox.

Start with PlunkCheck SPF record

Frequently asked questions

What is an MX record?

An MX (Mail Exchanger) record is a DNS record that specifies which mail servers are responsible for receiving email for a domain. When someone sends an email to you@yourdomain.com, the sending mail server looks up the MX records for yourdomain.com to find where to deliver the message.

What does the MX priority number mean?

The priority number (also called preference) tells senders which mail server to try first. Lower numbers = higher priority. A server with priority 10 is tried before one with priority 20. If the primary server is unavailable, senders retry with the next highest priority server. Equal priority values means senders choose randomly — this is sometimes used for load balancing.

Do I need more than one MX record?

It's strongly recommended. A single MX record means email will bounce or queue during any outage. Adding a secondary MX (typically your mail provider's backup server, or a service like Google MX backup) ensures email is accepted even if your primary server is temporarily down.

Why would email delivery fail even if MX records are correct?

Several reasons: the mail server the MX points to may be down or unreachable on port 25; your IP or domain may be on a blacklist; SPF, DKIM, or DMARC might be misconfigured causing rejection; or the receiving server may be filtering based on content. MX records are just the first step — authentication records and reputation matter too.

Can I change my MX records without losing email?

Yes, with care. Lower your TTL to 300 seconds a day before making changes so the change propagates quickly. Add the new MX records before removing the old ones. Wait for propagation (typically 5–30 minutes with a low TTL), confirm the new server is receiving, then remove the old records and restore your TTL.