Open your Exchange 2007 PowerShell and execute these commands:

set-service msExchangePOP3 -startuptype automatic

start-service -service msExchangePOP3

set-service msExchangeImap4 -startuptype automatic

start-service -service msExchangeImap4

Forward Ports through your Firewall

IMAP4 - Forward ports 993 (Secure) and 143 to your Exchange server (not your edge server).
POP3 - Forward ports 995 (Secure) and 110.

That's it!  Now go configure your IMAP4 or POP3 clients.  From your BlackBerry choose "Personal Email Set Up" and follow the instructions.  Sending email is pretty much instant, but receiving email takes an average of 15 minutes.