Failure audit every few minutes for pop3 users

I have exchange 2003 with a handful of pop3 users.  They retrieve email ok but I notice that when they have Outlook open I get periodic "faiure audits" error 680 user does not exist in the security log.  It doesn't seem to affect anything, but I'm concerned about security on these accounts.  Whats the deal with pop3 on exchange?  Thanks.
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atheluConnect With a Mentor Commented:
Sounds like the connection is being continually validated, which is typical, but that the connection is attempting a preffered authentication method first (ie ntlm/kerberos) and when that fails, it resorts to basic. That is why you see the logon failure message, but the users still successfully authenticate. Similar to what vahik was saying, there should be a successfull log on message right after the failed attempt in the log.

Take a look at your POP3 connector on the back-end server. I am sure that it has simple authentication enabled, and one of its options will be NTLM.  if the NTLM authentication is failing (which it will unless connected on the local network) then the users credentials will be passed in basic (clear text).  To test whether this is the case, you could remove the check box from the basic authentication box, and i assume the clients would then fail to be able to retrieve mail.

I would HIGHLY recommend installing a SSL cert on the server and requireing SSL connections for POP3 and IMAP4. I cannot say this enogh. The users would be forced to make a change in the outlook settings to use the SSL ports, but that is a small price to pay for the increased security.
could you post a copy of the actual event message?
wburke121Author Commented:
Event Type:      Failure Audit
I only get this error for accounts that use pop3 on our exchange 2003 server

Event Source:      Security
Event Category:      Account Logon
Event ID:      680
Date:            5/2/2005
Time:            11:28:56 AM
User:            NT AUTHORITY\SYSTEM
Computer:      <<deleted for security reasons>>
 Logon account:      <<deleted for security reasons>>>
 Source Workstation:      <<deleted for security reasons>>
 Error Code:      0xC0000064

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680 failure means some one used wrong users name password and failed to authenticate
against ur domain....there must be one success 680 right after for the same user if it was
a mistake...
wburke121Author Commented:
No, the users made no mistake and is actually getting pop3 mail from the exchange server.  We have 3 users who use pop3. It works, but while they have Outlook open on their PCs, either locally or remotely, this error shows up every 10 minutes on the Exchange server.
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