How to Check if SMTP Port 25 is Blocked

You can run a simple test to see if your ISP is blocking port 25.

Open terminal and type below command.( for windows: Start >> Run >> Type ‘cmd’)

telnet 25

Replace with your domain name.

If your ISP is blocking port 25 you will not get a response back. However if it isn’t blocking port 25 you will see an output similar to the one below.

stefin@fwhwin:~$ telnet 25
Connected to

Escape character is '^]'. ESMTP Exim 4.82 #2 Thu, 04 Sep 2014 05:34:20 +0000
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.

About Annie

I've been working in Technical Section for over 10 years in a wide range of tech jobs from Tech Support to Software Testing. I started writing blog for my future reference and useful for all.