How to check if SMTP port 25 is blocked.

How to check if SMTP port 25 is blocked?

The default port used for SMTP connections is port 25. One of the most common reasons that you are unable to send messages is that your internet service provider (ISP) is blocking this port. This is why using an alternative SMTP port is then recommended.

Here's how to check, depending on your operating system, if your ISP is blocking port 25:

Check port 25 in Windows

Click the Start menu button, usually located on the lower left corner of the screen. There is a tab called "Run." Click on it and a new window will appear. In the text field of this window, type cmd then hit the "Enter" key. Another window will open. It is the so-called "MS-DOS prompt" or "command prompt". Just type the following (below) command in the command prompt window and press "Enter":

telnet my-domain-name.com 25

Check port 25 in Mac OS

Every Mac OS comes with a pre-installed terminal emulator. The terminal is a tool that allows you to execute commands from the command line. Usually the terminal is located under your Mac HD -> "Applications" directory -> Utilities sub-directory. When the window opens, you will see a command line with a blinking cursor on it so you can start typing right away. Just type in the following (below) command and press "Enter":

telnet my-domain-name.com 25

Check port 25 in Linux

Open your favorite terminal emulator and enter the following command (below) to check the connection on port 25 to your website:

telnet my-domain-name.com 25

Checking the results of the 25 port

If the test is successful, you will receive a message like this:

220 smtp.myhostingpartner.com

If you get a message that the connection is denied then we recommend that you use the alternate port for your SMTP connection.

What is the alternate SMTP port and how do you configure an email client to use it?

The reason most ISPs block the default SMTP port 25 is because it is used for sending unsolicited emails.

Fortunately, email hosting providers like MijnHostingPartner.nl offer an alternative SMTP port for their clients' use.

The alternate SMTP port that all MHP customers can use is port 26.

Information on how to change the SMTP port for the most popular email clients can be found in our frequently asked questions.

If you want to use an alternative SMTP port for any reason, as well as unlimited mail accounts and a stable mail service then you can sign up for an account with MijnHostingPartner.nl. Our servers have been modified using "state-of-the-art" spam protection system with ACL filters that ensure that spam is flagged so that you can decide what to do with it.