SMTP Server Test
Connect to a mail server and read its greeting and advertised capabilities, including STARTTLS, AUTH and message size limit. Free SMTP check.
This check runs from our server, not from your browser, and is rate limited. Nothing you enter is stored. Private and internal addresses are refused on purpose.
What this tool is for
Opens a connection to a mail server, reads the greeting and asks what it supports, then hangs up. Nothing is sent and no message is attempted. Useful to confirm that a server is reachable on the port you expect and that it offers STARTTLS, which it should. This is one of the few tools here that needs a server, because the question is about the internet rather than about your data. The request is made from our server, rate limited, and nothing you enter is stored.
How to use it
- Enter the mail server hostname, usually the value of an MX record.
- Pick the port: 25 between servers, 587 for submission.
- Read the greeting and the capability list.
Frequently asked questions
Nothing answers on port 25.
Many networks and cloud providers block outbound port 25 to fight spam. A timeout here often says more about the route than about the mail server.
Does no STARTTLS mean mail is unencrypted?
On that port, yes: without STARTTLS the session is plain text. Modern servers should offer it on 25 and require TLS on 587.
Can this tell me if an address exists?
No, and it deliberately does not try. Probing recipients is what spammers do, most servers lie about the answer, and doing it gets you blocklisted.