MX Record Checker

Perform an advanced DNS lookup to validate your domain's Mail Exchanger records in real-time. Identify misconfigurations, verify priority weighting, and ensure RFC 5321 compliance.

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What Is an MX Record?

A Mail Exchanger (MX) record is a fundamental DNS resource record (RFC 1035 / RFC 5321) that maps a domain to the Message Transfer Agents (MTAs) responsible for receiving its email. Each record carries a preference value that controls failover and load-balancing priority across multiple mail servers.

Why It Matters

Without valid MX records, inbound email cannot reach your servers. Misconfigured records cause bounced messages, silent delivery failures, and broken SPF / DMARC pipelines.

Common Mistakes

Pointing MX to a CNAME (violates RFC 2181), missing secondary failover hosts, and using private IP ranges are the top causes of inbound mail failure.

DOMAIN_QUERY

MX_RECORDS_FOUND

PRIORITY_10

HOST_REACHABLE

MX_VALIDATION_ENGINE

RFC_COMPLIANT

How It Works

Enter Domain

Type your root domain or subdomain into the MX lookup tool above.

DNS Query

Our engine queries authoritative DNS servers for all MX records in real-time.

Review Results

Inspect hostnames, priority values, and reachability of each mail server.

Fix & Verify

Follow our recommendations to resolve misconfigurations and re-test.

RFC-Compliant DNS Resolution

Executes deep DNS queries to verify that your MX records strictly adhere to RFC 1035 and RFC 2181 standards. Detects illegal CNAME aliases in MX targets and ensures all records resolve to valid A or AAAA records, preventing fundamental routing failures.

Priority & Redundancy Analysis

Evaluates the preference values of your Mail Exchangers to confirm proper load balancing and failover architecture. Identifies single points of failure and verifies secondary MTAs are correctly weighted to handle SMTP traffic if the primary node goes offline.

SMTP Target Validation

Validates the endpoints specified in your MX records to ensure they point to operational Message Transfer Agents. Checks for common misconfigurations like resolving to localhost (127.0.0.1) or private IP spaces which can silently blackhole inbound mail.

Real-Time Query Execution

Bypasses local caching to perform authoritative DNS lookups directly against root and TLD nameservers. Ensures you receive the most current configuration data for accurate, real-time troubleshooting of mail flow disruptions.

Advanced Error Diagnostics

Provides granular, technical error reporting for misconfigurations, including null MX records (RFC 7505), unresolvable hostnames, and invalid syntax. Empowers network administrators with actionable insights to remediate DNS flaws instantly.

Security & Deliverability Impact

Analyzes your MX architecture in the context of broader email security. Highlights how invalid mail routing can affect sender reputation and interoperate poorly with SPF and DMARC enforcement mechanisms, securing your inbound vector.

Frequently Asked Questions

What is the correct priority for an MX record?

MX record priority (preference) determines which MTA is contacted first, as defined in RFC 5321. Lower numbers mean higher priority. Your primary mail server should have the lowest value (e.g., 0 or 10) and secondary servers higher values (e.g., 20, 30) for failover. Equal priorities imply load balancing via DNS round-robin.

Can an MX record point to a CNAME?

No. According to RFC 2181 (Section 10.3), the target of an MX record must resolve directly to an A or AAAA record, not a CNAME alias. Pointing an MX to a CNAME causes unnecessary DNS overhead and can lead to mail loops or delivery failures in strict SMTP implementations.

What is a Null MX record and when is it used?

A Null MX record (RFC 7505) is formatted as '0 .' It signals to remote MTAs that the domain accepts no mail, allowing them to instantly reject messages without attempting connections or retries. It is used for parked domains or domains that should never receive email.

How does MX validation interact with DMARC and SPF?

MX records handle inbound routing, but some strict receiver policies check the envelope sender's domain for valid MX records as a basic anti-spoofing measure before processing SPF or DMARC. An invalid or missing MX record can cause your domain to be flagged as suspicious.

Why is my MX checker reporting an 'Unresolvable Hostname' error?

This error means the MTA hostname in your MX record does not have a valid A or AAAA record in DNS. Without a resolvable IP address, remote SMTP clients cannot establish a TCP connection on port 25 to deliver mail, resulting in hard bounces.

Does my domain need multiple MX records?

While a single MX record is technically sufficient, multiple MX records are strongly recommended for fault tolerance. If the primary MTA goes offline, sending servers automatically queue and retry delivery to secondary MTAs, preventing immediate mail rejection.

How quickly do changes to an MX record propagate?

DNS propagation for MX records is governed by the TTL (Time to Live) value set in your zone file. If TTL is 3600 seconds (1 hour), it can take up to one hour for recursive resolvers globally to expire their cache and pick up the updated routing information.

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