SMTP Check

Test bounded TCP reachability to a domain mail exchanger without sending a message.

Health score--Bounded SMTP probe

Signal checklist

The result shows selected MX host, checked address, port, TCP status and antiabuse limits.

Enter a domain and choose an allowed SMTP port to test whether a selected MX host accepts a TCP connection.

The result shows selected MX host, checked address, port, TCP status and antiabuse limits.

The API resolves MX first, validates public addresses, checks at most one address and uses a short timeout.
Open means the runtime established TCP; closed or timeout can be firewall, provider policy or route-specific.
The free check does not send EHLO, STARTTLS, AUTH, RCPT, DATA or any message content.

Free check: One MX-based TCP probe on allowed SMTP ports with no EHLO, recipient or message sending.
Optional account features: Uptime monitoring, incident timelines, alerting, multi-region checks and status reports.

Builders are active for SPF and DMARC. DKIM, MX, SMTP, reputation and header pages stay guide-only because provider setup varies.

Chain SPF, DKIM, DMARC, MX, SMTP, reputation and header checks without storing the target.

Support

Use the result first. Support and promotional areas stay separate from the useful result.

Choose an amount before the secure payment page opens.

Enter a domain and choose an allowed SMTP port to test whether a selected MX host accepts a TCP connection.

The API resolves MX first, validates public addresses, checks at most one address and uses a short timeout.

Open means the runtime established TCP; closed or timeout can be firewall, provider policy or route-specific.

A provider may allow port 25 from the internet but block 587 unless authenticated submission is configured.

Testing arbitrary SMTP hosts can become abusive, so MailHealth only checks MX-derived public hosts.

Verify MX records first, then compare the SMTP result with provider status and firewall rules.

The free check does not send EHLO, STARTTLS, AUTH, RCPT, DATA or any message content.

Does this send an email?

No. The free SMTP check only attempts a bounded TCP connection.

Why not scan every port?

MailHealth is not a port scanner; SMTP checks use a narrow allowlist and MX-derived hosts.