XCON: POP3 and IMAP4 Clients Cannot Log On to Exchange Server, and Event ID 13003 Occurs

Post Office Protocol 3 (POP3) and Internet Message Access Protocol, Version 4rev1 (IMAP4) clients may not be able to log on to Exchange 2000 Server or Exchange 5.5 Server. Additionally, you may receive an event message that is similar to the following event message in the Application log of Event Viewer:

This behavior may occur if the Exchange Server mailbox alias is different from the Microsoft Windows user account name.

To resolve this issue, use one of the following methods, as appropriate to your situation:

• Use the following format for the user account name on the client, where Domain is the name of the domain, UserName is the Windows user account name, and Mailbox is the Exchange Server mailbox alias:
  Domain\UserName\Mailbox
  NOTE: The Domain\UserName\Mailbox format is used by and works with Microsoft Outlook Express clients. Results may vary with other clients.
  
  -or-
  
  
• Change the Exchange Server mailbox alias to use the same name as the Windows user account name. By doing so, users require only one account name.
  
  -or-
• Create a second Exchange Server mailbox alias that matches the Windows user account name.

For additional information about how to troubleshoot a similar issue, click the article numbers below to view the articles in the Microsoft Knowledge Base: