How to check if SMTP port 25 is blocked?

November 30, 2010 / FAQs

The standard port utilized for SMTP connections is 25. One of the most useful causes for not being capable of sending messages is that your Internet service provider blocks this port. This is why utilizing an optional SMTP port is highly recommended.

Here’s how to, depending on your OS, check whether your ISP blocks port 25:

Check port 25 in Windows

  1. Click on the Start menu button (generally present at the lower left corner of the screen)
  2. Click on the “Run” tab from the menu, Click on it (a new window will pop up).
    You require to type cmd into text field
  3. Press the “Enter” key Other window will open. It is the so called “MS-DOS prompt” or “command prompt”
  4. Just type the following command in the command prompt window and press “Enter”: telnet 25

Check port 25 in Mac OS

Every Mac OS is delivered with a preset up terminal emulator(tool which permit you to execute commands from the command line). Generally, the terminal is present under your Mac HD -> “Applications” directory -> Utilities sub-directory. When the window opens, you will find a command line with a flashing cursor on it so you can start typing right away. Just type the following command and press “Enter”:
telnet 25

Check port 25 in Linux

Open your favorite terminal emulator and execute the following command in order to check the connection on port 25 to your website:
telnet 25

Results from the 25 port check

If the test is successful, you should receive a message similar to this one: ESMTP Exim 4.63 #1 Wed, 18 Apr 2008 07:17:30 -0500
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.