This is a quick resolution to help resolve the common "My ISP is blocking SMTP port 25 issue on your personal vps or dedicated server". Here is how it's done.
First you will need to login to WHM (Web Host Manager) you can locate this information in your initial welcome email sent out when you ordered your server.
You access it like this: https://<myserversipaddresshere>/whm
This will bring up a login box, in here you'll enter your server's root username & password details to enter into WHM. Now that your logged into WHM, scroll down to the "Service Manager" link section under the Service Configuration section of the WHM tool.
Once there, scroll down and you'll see the option to select "Exim on another port" make sure to tick both checkmark boxes and enter the desired alternate port number to run Exim SMTP on. This will enable Exim to now relay mail on the inputted port number.
Save the changes and you will be done.