How to check is Port 25 blocked by your ISP ?

[Dipak Bhoi]

Hello guys,

This post will help you how you can check to see if Port 25 is blocked on your network or not. Many email clients and services use port 25 for SMTP to send out emails, an ISP (Internet Service Provider) may block port 25 in order to prevent spamming by theirs clients.

Type the following command into command prompt/terminal.

telnet yourdomain.com 25

If Port 25 is not blocked, you will get a successful 220 response as like below.

Trying xx.xx.xx.xxx....
Connected to yourdomain.com.
Escape character is '^]'.
220 c01.server.com ESMTP Exim 4.63 Tue, 24 Jun 2014 13:45:04 -0700

If Port 25 is blocked, you will get a connection error or no response at all lime as below.

Trying xx.xx.xx.xxx...
telnet: connect to address xx.xx.xx.xxx: Connection refused
telnet: Unable to connect to remote host

Note : You may also choose to use the alternate Port 587 if Port 25 is blocked.