Configuring your Exchange account as a IMAP account will provide ONLY e-mail functionality using your Exchange account. When using IMAP, you will not be able to access the additional features of Exchange such as the calendar, tasks, Public Folders, etc.
For help on setting up your Exchange account for full functionality, please reference on of the following articles.
Set up an Exchange Account in Entourage 2008
Set up an Exchange Account in Outlook 2003
Set Up an Exchange 2007 Account in Outlook 2007
To configure a IMAP Server for your Exchange e-mail you will need the following information.
Server Type: IMAP
Incoming Server: imap.exchange.1and1.com
Incoming Server Port: 143
Incoming Server Port (using SSL): 993
Outgoing Server: smtp.exchange.1and1.com
Outgoing Server Port: 25 or 587
Outgoing Server Port (using SSL): 25 or 587
Account name/User name: Can be found in your Control Panel under MS Exchange Account (e.g. e123456789)
Password: Your Exchange account's password