Set your SMTP Port back to 465 so in case you forget it due to trying different scenarios.
Just to confirm, you are using POP3 & not IMAP4 correct? and have you tried it with Secure (SSL) Off
You must also use your full email address e.g. richard.branson@blueyonder.co.uk
Finally, check that any antivirus you are using such as McAfee isn't blocking you from sending mail.
After that I have no idea. You should contact your provider.