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.
