MX Record Checker
Fast, accurate, and free online MX Record Checker tool that runs directly in your browser.
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Other tools you may find usefulChecking MX Records - Email DNS Diagnostics
MX (Mail Exchange) records point to the servers responsible for receiving mail for a domain. Incorrect MX configuration = email not delivered or sent to spam. The tool verifies domain MX records, checks priorities and compares them with the configuration of popular email services.
What are MX records
MX record: A DNS entry pointing to the SMTP server that receives email for a domain. Format: priority (number) + hostname. Lower priority = higher priority. Google Workspace example: MX 1 aspmx.l.google.com, MX 5 alt1.aspmx.l.google.com, MX 5 alt2.aspmx.l.google.com, MX 10 alt3.aspmx.l.google.com. Multiple MX records = redundancy (failover).
MX Priorities and Redundancy
The email sending server tries MX with the lowest priority (value 1 > value 10). If unavailable: goes to the next one. Same priority value: random selection (load balancing). Recommended configuration: min. 2 MX records from different providers for redundancy. If only 1 MX: failure = no mail.
MX for popular services
Google Workspace: aspmx.l.google.com + alt1-4. Microsoft 365: domain.mail.protection.outlook.com. OVH: mx1.mail.ovh.net (priorities 1/5/50). Hetzner: mx.hetzner.com. Zoho: mx.zoho.eu (EU), mx.zoho.com. FastMail: in1-smtp.messagingengine.com. ProtonMail: mail.protonmail.ch. Self-hosted Postfix: your own hostname.
Diagnosing email problems
Email not arriving: check MX records (dig MX domain.pl). Check the A record of the MX host (must point to IP). Check SPF (TXT: v=spf1...). Check DMARC (TXT: _dmarc.domena.pl). Check blacklists (MXToolbox blacklist check). Check the server's SMTP logs: /var/log/mail.log. Test shipping: mail-tester.com.
FAQ
How to check MX records in terminal?
dig MX domaina.pl (Linux/Mac, dnsutils package). nslookup -type=MX domain.pl (Windows). host -t MX domain.pl. TTL reading: dig MX domain.pl +nocmd +noall +answer. Check the A record of the MX server: dig A aspmx.l.google.com. PowerShell: Resolve-DnsName -Type MX domain.pl.
Why does email go to spam?
No SPF or fail. No DKIM (email signature). No DMARC or p=none. IP Reputation: Blacklisted server. Content spam filters: keywords. No reverse DNS (PTR record) for the sending server IP. Bounce rate too high. Spam complaint rate too low. Check: mail-tester.com, MXToolbox Super Tool.
What is the difference between an MX record, an A record, and a CNAME record?
A record: maps hostname to IP (e.g. mail.domain.pl → 1.2.3.4). MX record: indicates the mail server for the domain (with priority). CNAME: alias name (e.g. www → domain.pl). MX must point to A record, NOT CNAME - the RFC standard prohibits MX pointing to CNAME (although many servers accept it, it is not valid).
How long does it take to propagate MX records?
Record TTL: min. 300s (5 min) to 86400s (24h). MX change: propagation globally 24-48 hours. Practically: most servers see the change in 1-4 hours. Before migrating email: lower the TTL to 300s for a few days. After migration: raise TTL. Check propagation: dnschecker.org → select MX type.
How does MX fallback work when the main server is unavailable?
The sending server tries in order: MX priority 1 → timeout → MX priority 5 → etc. Retry queue: the sending server retries for 4-5 days. Bounce (NDR): Sent after exhausting attempts. Temporary error (4xx): server retrying. Permanent error (5xx): immediate bounce.
Related tools: SPF record generator, DNS record checker and email header tester.