You can verify whether your ISP (Internet Service Provider) has your STMP PORT 25 blocked in the following manner:
1. Check port 25 in Windows
Click on the Start menu button, usually located at the lower left corner of the screen. There is a tab called "Run". Click it and a new window will pop up. In the text field of this window you need to type cmd and then press the "Enter" key. Another window will open. It is the so called "MS-DOS prompt" or "command prompt". Just type the following command in the command prompt window and press "Enter":
telnet my-domain-name.com 25
2. Check port 25 in Mac OS
Each Mac OS is delivered with a preinstalled terminal emulator. The terminal is a tool which 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 flashing cursor on it so you can start typing right away. Just type the following command and press "Enter":
telnet my-domain-name.com 25
3. 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 my-domain-name.com 25
Results from the 25 port check
If the test is successful, you should receive a message similar to this one:
220-serv01.siteground173.com 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.
Once you have determined that your PORT 25 is blocked, it was probably due to SPAM, which may not have been of your own doing. What you can do is change your ISP, use a proxy server or why not go to the abdicar.com Customer Portal and switch over to a VPS or Dedicated server from abdicar.com? You can pay the managing fee and change your STMP PORT and solve your problem all at once!