For this you will need the following:

• Your BT email address
• Your BT email password
• Your Castus email address
• Your Castus email username
• Your Castus email password

The procedure

1. Add a new email account, by going to Tools > E-mail Accounts. Click Add a new e-mail account. Click Next.
2. Select POP3. Click Next.
3. Fill out your name.
4. Fill out your Castus email address.
5. Enter pop.castus.co.uk in the Incoming mail server box.
6. Enter mail.btinternet.com in the Outgoing mail server.
7. Enter your Castus email username in the User Name box.
8. Enter your Castus email password in the Password box.
9. Click More Settings.
10. Click on the Outgoing Server tab.
11. Tick the box: My server requires authentication
12. Click on Lon on using
13. Enter your BT email address as the Account name
14. Enter your BT email password as the Password
15. You can now test your account settings. Click the Test Account Settings button.
16. If you have any problems double check your usernames and passwords – this is the cause of 99% of email set up problems.
17. Once OK, click Next.
18. Click Finish.

All done.