Check MX records, SMTP reachability, SPF, DMARC, DKIM, MTA-STS, TLS-RPT, reverse DNS and DNSBL status.
The check runs from the InetTools server. DNSBL providers may limit public queries, so blocked means the DNSBL query was limited, not that the IP is listed.
Quick start
Inspect mail DNS and reachability with a downloadable report.
1
Enter a domain or mail server IP
2
Choose SMTP and DNSBL checks
3
Review DNS, warnings and report scope
MX Toolbox online
Run mail diagnostics for a domain or IP address. The tool checks MX records, mail server IPs, SMTP banner, STARTTLS, SPF, DMARC, optional DKIM selector, MTA-STS, TLS-RPT, reverse DNS and several DNSBL lists.
Use it to troubleshoot mail delivery, domain authentication, mail server reachability and common DNS configuration problems from one page.
✓Run the check after changing MX, SPF, DMARC, DKIM or moving a mail server.
✓Missing MX records are not always wrong for a domain without mail, but they are normally required for receiving email.
✓SPF and DMARC help receivers understand which servers may send mail for the domain.
✓DKIM is checked by the selector you enter, so the selector can differ between mail providers.
✓DNSBL checks depend on external blocklists and may be rate-limited by those providers.
✓The SMTP probe checks port 25 reachability from the InetTools server, but it does not send mail or test open relay.
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