MX record discovery
Fetches all published MX records and sorts by priority — lowest number tried first.
Free tools
MX lookup — mail exchange records & routing priority
Enter any domain to look up MX records, priority values, mail hostnames, and resolved IP addresses for inbound mail routing context.
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At a glance
- What it is
- DNS MX lookup with priority sorting, per-host IP resolution, null MX detection, and apex fallback hints.
- Who it is for
- Email operators, deliverability consultants, and MailFleet users auditing domain mail routing.
- Main capabilities
- MX table, priority badges, A/AAAA resolution, null MX, apex fallback, captcha, rate limits.
- Platforms
- Browser-based diagnostic on mailfleet.app with server-side DNS checks when the live service is available.
- Responsible use
- Reads public DNS only. Does not test SMTP or mailbox availability on MX hosts.
MX record lookup
Query mail exchange records, sort by priority, and resolve each host to IP addresses.
DNS query
MX domain.com
Lower priority number = tried first · Equal priorities may load-balance
Capabilities
Understand inbound mail routing
See where a domain receives mail, which host is primary, and whether DNS is configured correctly.
Hostname IP resolution
Resolves each MX exchange to A and AAAA addresses for routing troubleshooting.
Priority visualization
See primary vs backup hosts and equal-priority load balancing at a glance.
Null MX detection
Identifies RFC 7505 null MX (0 .) domains that do not accept inbound mail.
Apex fallback hint
When no MX exists, checks apex A/AAAA per RFC 5321 fallback behavior.
Abuse-resistant
Image captcha, session verification, and per-IP rate limits for public use.
How to use
Five steps to read MX records
- 1
Enter domain
Use any domain — customer, competitor, or your own — to see inbound mail routing.
- 2
Solve captcha
Complete the image challenge before querying DNS.
- 3
Review MX table
Lower priority numbers are preferred. Multiple equal priorities may load-balance.
- 4
Check host IPs
Confirm each exchange resolves — broken hosts block inbound delivery.
- 5
Context for outbound
MX is inbound routing; use SPF/DKIM/DMARC tools for outbound authentication.
What are MX records?
Mail Exchange (MX) DNS records tell sending servers where to deliver email for a domain. Each record has a priority (preference) and a hostname of the receiving mail server.
Senders try lower priority numbers first. If multiple records share the same priority, mail may be load-balanced between them.
MX vs outbound deliverability
MX records control inbound delivery to your domain. They do not authorize outbound sending — that is SPF, DKIM, and DMARC.
MX lookup is still useful when migrating mail hosts, auditing customer domains, or verifying DNS after a provider change.
- Inbound: MX points to Google, Microsoft, or your mail server
- Outbound: SPF lists sending IPs; DKIM signs messages; DMARC sets policy
- Null MX (0 .): domain explicitly does not receive mail
What this tool does not do
This tool reads public DNS only. It does not test SMTP connectivity or mailbox availability on the MX hosts.
DNS propagation delays can make recent changes invisible until TTL expires.
Key takeaways
- Lower MX priority numbers are tried first by sending servers.
- MX routes inbound mail — outbound auth is SPF, DKIM, and DMARC.
- Null MX (0 .) means the domain does not accept email.
- Unresolved MX hostnames will break inbound delivery to that host.
For regulatory context on commercial email in the United States, see the FTC CAN-SPAM compliance guide.
Delivery note: MailFleet helps users manage campaigns through their own sending providers. Delivery outcomes depend on sender reputation, DNS authentication, content quality, recipient engagement, list quality, provider rules, and mailbox filtering systems.
MX lookup FAQ
No. MX routes inbound mail. Outbound deliverability depends on SPF, DKIM, DMARC, content, and sender reputation.
Get started
Send outbound mail with MailFleet
Desktop sending with provider profiles — pair MX context with SPF, DKIM, and DMARC checks.
Available on
- Windows 10+
- macOS 12+
- Linux (DEB & RPM)
Same desktop experience across every platform — one workflow for your entire team.