SMTP Test
Inspect mail server connectivity and capabilities.
An SMTP test opens a TCP connection to a mail server's port from a remote probe to confirm it is reachable from the internet. It answers reachability; full protocol negotiation and authentication are a separate matter.
Start a check
Public internet targets onlyResults
Ready when you are
Enter your details above and run the tool.
How SMTP Test works
What it does
Inspect mail server connectivity and capabilities.
What you get
Mail port reachability; protocol capabilities require the SMTP probe service.
Live data sources
The target is sent to a network provider. Results include their source; timeouts and unavailable data are clearly marked.
What if a check cannot finish?
Confirm your input and try again. A timeout, blocked request, or unavailable provider is not proof that a domain is broken. Internet measurements and third-party services have limits.
SMTP Test — frequently asked questions
Which SMTP port should I test?
587 for authenticated submission from clients, 465 for implicit TLS, and 25 for server-to-server delivery. Most consumer networks block outbound port 25.
The connection fails but my mail works. How?
Your provider may accept connections only from specific networks, or a firewall may allow your server while blocking the probe. Reachability from one place does not generalise.
Does this test whether mail will be delivered?
No. It tests that the port answers. Delivery also depends on authentication, SPF/DKIM/DMARC alignment, content filtering and sending reputation.