Email Port Checker
Check which email ports are open on a domain's mail server — SMTP 25/465/587/2525 and IMAP/POP — with real TCP connections. Free email port checker.
Check email ports
Enter a domain. We resolve its mail server and test which email ports are open.
What this port checker does
Common use cases
- 1Confirming a mail server is reachable
- 2Choosing which submission port to configure
- 3Diagnosing a blocked outbound port 25
- 4Auditing which mail services are exposed
- 5Checking a firewall change took effect
- 6Verifying IMAP/POP access is available
Related tools
About email ports
Email uses several well-known TCP ports. 25 carries server-to-server relay, 587 is the modern submission port (with STARTTLS), and 465 is implicit-TLS submission. Retrieval uses 143/993 (IMAP) and 110/995 (POP3).
This checker opens a real connection to each port on the domain's mail server and reports which respond. Bear in mind that a "closed" result may mean a firewall is filtering the port rather than the server not listening — port 25 in particular is widely blocked for outbound traffic, so use 587 or 465 to send mail.
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Got Questions? We Have Answers.
Which ports does this checker test?
It tests the SMTP ports 25, 465, 587 and 2525, plus IMAP (143/993) and POP3 (110/995), by opening a real TCP connection to each on the domain's mail server.
What is the difference between the SMTP ports?
Port 25 is server-to-server relay, 587 is modern submission with STARTTLS, 465 is implicit-TLS submission, and 2525 is a common alternative when others are blocked.
Why does a port show as closed?
It may be genuinely closed, or a firewall may be filtering it. Outbound port 25 in particular is widely blocked, so a "closed" 25 is often a network block rather than a server issue.
Which port should I use to send mail?
Use 587 with STARTTLS for most clients, or 465 for implicit TLS. Avoid 25 for submission — it is for server-to-server relay and is frequently blocked.
Are these real connections?
Yes. Each port is probed with a live TCP connection at the moment you run the check — not looked up in a database.
What does the checker use for the host?
It resolves the domain's MX record and probes the mail server that actually handles the domain's email.