How to Change Port 25 in your email client
Sometime your ISP will block port 25 and prevent you from sending SMTP email on that port. Your email service provider may ask you to change the port being used to something other than port 25.
Most email programs have configuration settings like this:
Where on the Advanced Tab or similar depending on the email program in question there are settings for the outgoing SMTP server.
To change the SMTP port from 25 to 587 for example you just replace this:
Click OK and you are done.
It should be noted that the port number to use must be provided to you by your Email ISP.