This answer will explain how to set up Entourage with IMAP.
Click on Tools then Accounts.
Once on the Mail tab click on New.
Choose an account name and a name that will be displayed when someone receives your emails.
Enter your email address and username.
Your incoming mail server is: imap.123-reg.co.uk.
Your outgoing mail server is smtp.123-reg.co.uk.
Please note: If you are using 123-reg's SMTP server to send outgoing email, SMTP authentication must be turned on. If you are asked for a username and password, please use your mailbox username and password.