Instantly query MX (Mail Exchange) records for any domain. View mail server hostnames, priorities, TTL, and detected email provider — free, browser-only, no signup required.
✍️ Author: ToolsNovaHub•📅 Last Updated: 14 September 2026
Examples: gmail.comyahoo.commicrosoft.com
🔄 Querying DNS resolvers…
📧 MX Records for
Priority
Mail Server (Hostname)
TTL
Status
📊 MX Priority Visualisation
🔎 Raw DNS Response
🕒 Recent Lookups
No recent lookups yet.
📚 What Is an MX Record?
An MX (Mail Exchange) record is a DNS resource record type that specifies which mail server is responsible for accepting incoming email on behalf of a domain. When someone sends an email to user@example.com, the sending mail server queries DNS for the MX record of example.com, connects to the returned mail server hostname, and delivers the message. MX records are defined in RFC 1035, with their role in mail routing specified in RFC 5321.
MX records have two components: a hostname (the mail server's fully qualified domain name) and a priority value (a lower number = higher priority). Multiple MX records create fallback chains — if the primary server is unreachable, the sender automatically tries the next-priority server.
🔄 How MX Record Priority Works
Priority values are unsigned integers — smaller means higher preference. Standard practice:
Priority 0–5: Primary mail server (tried first)
Priority 10–20: Secondary / backup servers
Priority 50+: Tertiary fallback or spam filter bypass traps
Equal priorities: Load-balanced by sending MTA (random selection)
Google Workspace example: ASPMX.L.GOOGLE.COM at priority 1, ALT1 and ALT2 at 5, ALT3 and ALT4 at 10.
🔑 Common Email Providers & Their MX Patterns
Provider
MX Hostname Pattern
Primary Priority
Google Workspace
ASPMX.L.GOOGLE.COM
1
Microsoft 365
*.mail.protection.outlook.com
0
Zoho Mail
mx.zoho.com
10
ProtonMail
mail.protonmail.ch
10
Fastmail
in1-smtp.messagingengine.com
10
Mailgun
mxa.mailgun.org
10
SendGrid (Inbound)
mx.sendgrid.net
10
Amazon SES
inbound-smtp.*.amazonaws.com
10
🔧 Troubleshooting
⚠️ No MX records returned
Either the domain doesn't accept email at all, or mail is routed via an implicit MX (an A/AAAA record fallback per RFC 5321) — check the domain's A record too before assuming mail is broken.
⚠️ Mail bouncing despite valid MX records
MX records only route traffic to a mail server; delivery can still fail on the receiving server's own spam filtering, SPF/DKIM/DMARC checks, or a full mailbox — this lookup can't diagnose those independently.
⚠️ Priority values look reversed
Lower priority numbers mean higher priority in MX records — a record with priority 10 is tried before one with priority 20, which trips up people used to "higher number = more important" conventions elsewhere.
⚠️ Result differs from what you just changed in DNS
MX changes are subject to the record's TTL — resolvers worldwide keep serving the old value until their cached copy expires, so a change can appear "live" in one location and stale in another for a period entirely explained by caching.
🛡️ Use Cases for MX Lookup
📧
Email Deliverability Diagnosis
If emails bounce with "no MX record" or "host not found" errors, check MX records first. Missing, misspelled, or improperly prioritised records cause the majority of domain-level delivery failures.
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Email Infrastructure Reconnaissance
Security researchers use MX lookups to identify which email provider a target uses — vital for phishing simulation testing, email gateway configuration, and threat intelligence.
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Email Provider Migration
Before migrating from one email host to another, lower your MX TTL to 300 seconds. After switching, verify new MX records with this tool before restoring TTL to avoid mail loss during propagation.
🔒
SPF Record Validation
SPF's "mx" mechanism includes all MX hosts as authorised senders. Knowing your current MX records lets you verify your SPF policy accurately reflects your sending infrastructure. Use our SPF Lookup tool to check.
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Email Verification Pre-Check
Our Email Checker automatically queries MX records as the first step of verification. A domain without MX records cannot receive email — addresses there are automatically invalid.
📊
Redundancy Auditing
Professional email setups need at least 2 MX records. Single-MX-record domains risk total email loss during server outages. Use this tool to audit your MX redundancy configuration.
🔗 More Ways to Investigate Mail Infrastructure
For full DNS record inspection (A, TXT, NS, SOA), use our DNS Lookup tool. To verify your SPF authorisation policy, try SPF Lookup. For complete email domain health (MX + SPF + DMARC in one), use Email Checker. Learn the full email authentication picture in our guide: SPF vs DKIM vs DMARC.
ToolsNovaHub tools are built and independently maintained with a focus on accurate, no-signup network and security utilities. Spotted an error? Let us know.
🎓
Expert Tip
DNS and mail records can take up to 48 hours to fully propagate — if MX Lookup shows an unexpected result right after a change, wait and re-check before assuming misconfiguration.
⭐
ToolsNovaHub Pro Tip
Run MX Lookup from more than one network (office Wi-Fi + mobile data) to rule out local resolver caching before reporting a bug.
⚠️
Common Beginner Mistake
Editing a live DNS or mail record without noting the previous value first. Always save the old record from MX Lookup's output so you can roll back instantly if something breaks.
NXDOMAIN means the domain itself doesn't exist. If the domain exists but has no MX record, the query returns NOERROR with an empty answer — both cases mean email delivery will likely fail.
What is the difference between MX and A records? +
An A record maps hostname to IPv4. An MX record maps a domain to a mail server hostname — which then needs its own A/AAAA record. MX records must never point directly to an IP address.
What does MX lookup failure mean for email? +
If MX lookup fails, the sending MTA can't find where to deliver email. It retries for 72–96 hours before bouncing the message back to the sender with a delivery failure notice.
How do I verify MX records with dig? +
Run: dig MX example.com +short (Linux/Mac) or Resolve-DnsName example.com -Type MX (Windows PowerShell). This tool replicates that query in your browser.
Can I use the same MX for multiple domains? +
Yes. Multiple domains can point to the same mail server. The server uses the RCPT TO envelope address to route to the correct mailbox, regardless of how many domains it handles.
Is MX Lookup free? +
Yes — completely free, no sign-up, and we don't cap normal usage. Queries run through Google's public DNS resolver, which may itself rate-limit unusually heavy or automated traffic, but results otherwise appear instantly.