To send email, you generally use SMTP (Simple Mail Transfer Protocol) which uses TCP Port 25 to send its data. If you're having trouble sending emails on port 25 (the default SMTP port), try switching your SMTP port to port 26. Most ISPs are blocking port 25 to prevent spam accross the Internet, changing your SMTP port to 26 will solve this problem.
The other, more secure, way to send mail is authenticated SMTP on port 465.
Note: In MS Outlook you will need to use "user authentication" for outgoing mail and enter your email account settings.
