Email Server Test Test SMTP, IMAP and POP3 Mail Servers
Test your mail server from outside your network. This free email server test connects to your SMTP, IMAP or POP3 server from locations around the world, checks encryption and login, and times every step.
At a glance
- Protocols: SMTP, IMAP and POP3.
- Encryption: none, STARTTLS or SSL/TLS, with full certificate details; an invalid certificate is reported as an error.
- Ports: 25, 465, 587, 2525 (SMTP), 143, 993 (IMAP), 110, 995 (POP3).
- Steps timed: connect, greeting (banner), capabilities, TLS handshake and optional login.
- Safe: no email is sent or read; the session ends right after login.
- Global: test from up to 3 locations at once without an account.
- Free: no sign-up; export results as PDF, CSV or JSON.
How to test a mail server
- Enter the mail server host name, for example
mail.example.com. - Choose the server type: SMTP, IMAP or POP3.
- Choose encryption. The port is set automatically; change it if your server uses another one.
- Optionally enter a login and password to test authentication.
- Select up to three locations and click Run Test.
Which port and encryption should I use?
| Protocol | Plain / STARTTLS | SSL/TLS (implicit) |
|---|---|---|
| SMTP (submission) | 587 with STARTTLS | 465 |
| SMTP (server to server) | 25 | – |
| IMAP | 143 with STARTTLS | 993 |
| POP3 | 110 with STARTTLS | 995 |
Use SSL/TLS for ports that are encrypted from the start (465, 993, 995) and STARTTLS for servers that upgrade a plain connection (587, 143, 110).
What the email server test checks
- SMTP test: reads the 220 greeting, sends
EHLO, upgrades withSTARTTLSwhen chosen, and authenticates with AUTH PLAIN or LOGIN if you entered credentials. Then it sendsQUIT; no message is sent. - IMAP test: reads the greeting, requests
CAPABILITY, upgrades withSTARTTLSwhen chosen and logs in withLOGIN. - POP3 test: reads the greeting, requests
CAPA, upgrades withSTLSwhen chosen and logs in withUSERandPASS.
For each location you get the server IP and port, connect time, greeting time, login status and total time, plus the banner, the capability list, every server reply (with the password masked) and the TLS certificate.
Common mail server problems
- Connection timed out: the port is blocked by a firewall or the ISP. Many providers block outbound port 25, so test 587 or 465 for client submission.
- TLS or certificate error: the certificate has expired, doesn't match the host name, or the chain is incomplete.
- Authentication failed: wrong credentials, the auth method is disabled, or the server requires an app password.
- "No login method": the server doesn't offer authentication on this connection, often until STARTTLS is used.
Testing Microsoft Exchange and hosted mail
Exchange and hosted services such as Microsoft 365 support SMTP, and IMAP and POP3 when they are enabled. Test the host name your mail clients use, with the same port and encryption settings. ActiveSync and MAPI are not tested by this tool.
Related free tools
- Email Blacklist Check: check if your mail server's IP is on spam blacklists.
- DNS Trace Test: check your MX, SPF and other mail DNS records.
To monitor your mail server 24/7, including round-trip delivery checks with alerts, see Dotcom-Monitor.
Frequently asked questions
How do I test my mail server?
Enter the server's host name, choose SMTP, IMAP or POP3 and the encryption, optionally add a login, and run the test. It shows whether each location could connect, negotiate TLS and log in, and how long each step took.
Does the email server test send an email?
No. The test connects, checks the greeting, capabilities, encryption and optional login, and then disconnects. No email is sent, and no mailbox content is read.
How do I test an SMTP server?
Choose SMTP, set encryption to STARTTLS for port 587 or SSL/TLS for port 465, and enter credentials if you want to test authentication. A working server returns a 220 greeting, accepts EHLO and, with credentials, a 235 authentication reply.
How do I test IMAP?
Choose IMAP with SSL/TLS on port 993, or STARTTLS on port 143, and enter the mailbox login. The test shows the server's capabilities and whether the login succeeds.
Is it safe to enter my email password?
Logins are encrypted at rest and masked in results and shared links. As a best practice, use a dedicated test mailbox instead of a personal account.
Why does SMTP on port 25 time out?
Many networks and cloud providers block outbound port 25 to stop spam. Port 25 is for server-to-server delivery; mail clients should submit on port 587 (STARTTLS) or 465 (SSL/TLS).
Can I test Exchange or Microsoft 365?
Yes, over SMTP, IMAP or POP3, if those protocols are enabled for the account. ActiveSync and MAPI connections are not tested.
Last updated: