Here's a quick guide as to the settings that has worked for myself and others.
Assuming your using outlook 2007 (will be the similar for earlier version)
Email settings.
Your name: What you like to be known as
Email address:
email@blueyonder.co.uk
Account type: POP3
Incoming mail server: pop3.blueyonder.co.uk
Outgoing mail server: smtp.blueyonder.co.uk
Username:
email@blueyonder.co.uk
Password: email password
Tick remember password (optional but handy)
No Tick Require logon using Secure Password Authentication (SPA)
Click more settings
Outgoing server tab.
Tick My outgoing server (SMTP) requires authentication
Select either: Use same settings as my incoming mail server or Log on using, with the username and password filled in with the correct details
No Tick Log on using Secure Password Authentication
Advanced tab.
Incoming server (POP3): 995
Tick This server requires an encrypted connection (SSL)
Outgoing server (SMTP): 465
Tick This server requires an encrypted connection (SSL)