This article was previously published under Q296387
Users cannot log on and authenticate to their Exchange mailbox with the Post Office Protocol version 3 (POP3) in use.
If Diagnostic Logging is set to Maximum under Authentication in the POP3 service on the server that hosts the user's mailbox, the following events are logged in the Application log of the server:
Event Type : Error Event Source : POP3SVC Event Category : Authentication Event ID : 1022 Description : DS lookup for user User Logon Name, connecting from 172.16.30.31, failed with error 0x80040920.
Event Type : Error Event Source : POP3SVC Event Category : Authentication Event ID : 1011 Description : Authentication attempt from <IP Address of Client Machine> to User Logon Name has failed with error 0x52e
This behavior occurs because the value in the User Logon Name (Pre-Windows 2000) box does not match the value in the Mailbox Alias box.
To resolve this behavior:
Enter the logon credentials in the following format when you are connecting through POP3:
Verify that the Mailbox Alias value and the User Logon Name (Pre-Windows 2000) value match (if they do not, change them so that they do match):
In Active Directory Users and Computers, right-click the user account that you want to modify, and then click Properties.
On the Account tab, note the value in the User Logon Name (PreWindows 2000) box, which is the logon name or the samAccountName attribute.
On the Exchange General tab, note the value in the Alias box, which is the mailbox alias or the mailNickName attribute.
Note If the value in the User Logon Name (Pre-Windows 2000) box matches the value in the Mailbox Alias box, type the following logon credentials in the POP3 client: