These are pre-SP1 instructions. POP3 is supported in Exchange 2007 but not turned on by default. To turn it on (from the management shell):
1) Enable the service: Set-Service msexchangepop3 -StartupType automatic
2) Start the service: Start-Service msexchangepop3
3) Enable POP3 for mailboxes: Set-CASMailbox -identity mailboxname -PopEnabled $true
4) OPTIONAL To enable plain-text authentication: Set-PopSettings -LoginType PlainTextLogin
5) If you did number 4 then restart the service: restart-service msexchangepop3