Why user logon to POP3 mail server always failed?

This is using MS Exchange Server 2010. All my users either using OWA, OutlookAnywhere, or POP3. For overseas users, they are using POP3. However, no matter how I tried, change password, this user can't seem to logon successfully, with the following error:

+OK The Microsoft Exchange POP3 service is ready
USER userabc
PASS password
-ERR Logon failure: unknown usser name or bad password
-ERR Connection is closed.12

What went wrong with user/mailbox, how to resolve?

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Marwan OsmanCommented:
all users using pop3 are failed? or only for one user?
MichaelBalackAuthor Commented:
Hi Marwan,

Just the only one user.
MichaelBalackAuthor Commented:
Hi everyone,

I used POP3 commands to troubleshoot, here is how I go:

    a. open cmd
    b. telnet <pop3server IP> 110
    c. USER usera
    d. PASS password
    e. confirm user can not login

I used the same pop3 commands to check on other user credentials - login successfully

I open EMS, and using set-CASMailbox to set POPEnabled to $false, and then back to $true
I restarted the MS Exchange POP3 service. And to my surprise, user can login successfully.

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Marwan OsmanCommented:
Good job
MichaelBalackAuthor Commented:
Problem resolved and user can login to the pop3 server, after conducting the series actions as stated in my previous mail.
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