What Is MX Lookup?
An MX lookup (Mail Exchange lookup) queries the Domain Name System to find the mail servers responsible for receiving email for a domain. MX records are DNS records that specify which servers handle incoming email and in what order they should be contacted. When you perform an MX record lookup, you discover the complete email infrastructure behind any domain.
Our free MX record checker goes beyond basic record queries. It automatically detects email providers like Google Workspace, Microsoft 365, and ProtonMail, resolves mail server IP addresses, and analyzes priority configurations. Whether you need to check MX records for email troubleshooting, verify a migration, or audit email infrastructure, this tool provides complete mail exchange intelligence.
How to Check MX Records of a Domain (3 Methods)
There are several ways to check MX records and find mail servers for any domain. Our online tool is the fastest and most comprehensive method, but command-line alternatives are useful for system administrators.
nslookup -type=mx example.com. This queries MX records directly and shows all mail servers with their priority values. Available on all major operating systems.dig example.com MX +short for a quick MX record lookup, or dig example.com MX for full details including TTL values. For all DNS record types, use our DNS Lookup tool.What MX Lookup Reveals
When to Use MX Lookup
What Is an MX Record? Understanding Mail Exchange
An MX record (Mail Exchange record) is a DNS record type that directs email to the correct mail servers for a domain. Unlike NS records which delegate DNS authority, MX records specifically control email routing. Every domain that receives email must have at least one MX record.
How MX Records Work
- Sender's mail server queries DNS for the recipient domain's MX records
- MX records return mail servers sorted by priority (lowest number = highest priority)
- The sender connects to the highest-priority server via SMTP (port 25)
- If the primary server fails, the sender tries the next priority level
MX Record Example
This shows Google Workspace MX records with priority 1 (primary), 5, and 10 (backups). TTL is 3600 seconds (1 hour).
Popular Email Providers and Their MX Records
Our MX record checker detects 30+ email providers by analyzing MX record hostnames. Here are the most common email providers our tool identifies, along with their distinctive MX patterns:
Google Workspace
Most popular business email. MX pattern: aspmx.l.google.com with 5 servers at priorities 1, 5, 5, 10, 10.
Microsoft 365
Enterprise email with Exchange. MX pattern: *.mail.protection.outlook.com with single server at priority 0 or 10.
ProtonMail
Privacy-focused encrypted email. MX pattern: mail.protonmail.ch with backup mailsec.protonmail.ch.
Use our MX lookup tool to check MX records of any domain and discover which email provider powers it. Our tool also detects security gateways like Mimecast and Proofpoint that sit in front of the actual email provider. For complete domain intelligence, combine MX Lookup with our WHOIS Lookup and SPF Checker tools.
Email Infrastructure Best Practices
- Configure backup MX records for email redundancy and failover
- Implement SPF, DKIM, and DMARC records for email authentication
- Use appropriate TTL values (3600s recommended for MX records)
- Monitor mail server connectivity with regular MX lookups
- Verify MX records after any email provider changes or migrations
- Consider email security gateways (Mimecast, Proofpoint) for threat protection
- Test email delivery with DNS Propagation Checker after MX changes
- Keep mail server software and TLS certificates updated for security
Related DNS & Email Tools
Check all DNS record types (A, AAAA, MX, CNAME, TXT, and more).
Verify SPF records for email authentication and deliverability.
Check DMARC policy for email domain protection and reporting.
Check nameservers with provider detection and response times.
Find domain registration, registrar, and owner details.
Check DNS propagation worldwide after MX record changes.
How to Check MX Records — and Read What They Tell You
When you check MX records, two things matter: where mail goes (the exchange hostnames) and in what order(the priority numbers — lower wins). A healthy setup lists at least two records: gmail-smtp-in.l.google.com at priority 5 with alternates behind it means Google Workspace with built-in failover. A single record pointing at your web server's hostname usually means shared-hosting email — functional, but fragile. And a priority tie across two hosts means round-robin load balancing, which is intentional at providers like Microsoft 365.
Red flags this MX lookup surfaces instantly: no MX records at all (mail falls back to the domain's A record — often unintended), records pointing at unresolvable hostnames (mail bounces), stale records from a previous email provider after a migration, and CNAMEs in MX targets (forbidden by RFC 2181 and rejected by some senders).
Mail Not Arriving? Where MX Fits in Email Troubleshooting
MX records are step one of email delivery — but only step one. If your MX records look correct and mail still fails, walk the rest of the chain: verify the mail server actually accepts connections with the SMTP Test, then confirm your authentication records — SPF, DKIM, and DMARC — since missing authentication sends messages to spam even when routing is perfect.
After changing MX records, remember propagation: caches respect your records' TTL, so the old mail server can keep receiving for hours. Check how the change has spread worldwide with the global DNS lookup before assuming something is broken.