The following symptoms occur when you try to log on to the Administrator mailbox by using POP3 or IMAP4:

• The logon attempt fails, and you receive an error message that states that the user name is unknown or that the password is incorrect. For example, in an e-mail client such as Outlook Express, you will receive the following error message:
  
  Logon failure: unknown user name or bad password
  
  
• If you try to log on by using POP3, the following warning is logged in the Application log of the Client Access server:
  
  Event Type: Warning
  
  Event Source: MSExchangePOP3
  
  Event Category: General
  
  Event ID: 1005
  
  Description:
  
  Authenticated user Domain\Administrator attempts to access POP but is disabled for that protocol.
  
  For more information, see Help and Support Center at
  
  http://go.microsoft.com/fwlink/events.asp.
  
  
• If you try to log on by using IMAP4, the following warning is logged in the Application log:
  
  Event Type: Warning
  
  Event Source: MSExchangeIMAP4
  
  Event Category: General
  
  Event ID: 1005
  
  Description:
  
  Authenticated user Domain\Administrator attempts to access IMAP but is disabled for that protocol.
  
  For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
  
  

The Administrator account is blocked from accessing its mailbox by using POP3 or IMAP4. This behavior is by design in Exchange 2007 to enhance security for the Administrator mailbox.

Do not use POP3 or IMAP4 to connect to the Administrator mailbox. You must use Outlook or Outlook Web Access to access the Administrator mailbox.