The MX Lookup tool retrieves Mail Exchanger (MX) records for any domain — showing which mail servers accept incoming email for that domain and at what priority. Email routing, deliverability troubleshooting, anti-spam verification, and threat investigation all start with knowing exactly where email for a domain is being directed. MX records are among the most security-sensitive DNS records because unauthorized changes directly enable email interception and phishing.
When email to or from a domain fails or bounces unexpectedly, MX Lookup is the first diagnostic step. It confirms whether MX records exist, whether the mail server hostnames resolve to valid IPs (cross-reference with DNS Lookup), and whether priority values are configured correctly for your primary and backup mail servers.
Attackers who gain control of a domain's DNS (via registrar compromise or DNS hijacking) often change MX records to intercept incoming email — including password resets, banking notifications, and internal communications. Security teams should monitor MX records for all critical domains and alert on any change. For historical MX configurations, use Historical DNS Lookup — MX record history is one of its most queried features.
SPF records authorize which mail servers may send email on behalf of a domain. The 'mx' mechanism in an SPF record automatically authorizes all servers listed in the domain's MX records. MX Lookup lets you see exactly which servers are being authorized via the SPF 'mx' mechanism — critical for ensuring your SPF policy matches your actual sending infrastructure. Check both MX and TXT (SPF) records together via DNS Lookup.
Phishing domains frequently configure MX records to collect credentials submitted via fake login forms. Checking MX records on suspected phishing domains reveals if they're set up to receive email — a common signal that the domain is being actively operated for malicious purposes rather than just parked.
A domain with no MX records will fall back to the A record for email routing, or reject delivery entirely. Always verify both MX and A records when troubleshooting email delivery problems.
