Saw a lot sync error on MS Outlook for Exchange 2010 server

This is using a Exchange server 2010. Users using outlook to send/receive mails. However, there is a user told me that she saw 5000+ mails stuck in a folder called "Sync error". There are a lot of error log with the last 2 lines of error code as follows:

    Microsoft Offline address book
    0x80072EE7

The only check I did was to go to the console > server - Client access, double click the Default offline address distribution, and confirm the internal and external url:

   internal url: http://mailsvr.abc.local/oab
   External url: https://mail.abc.com/oab

I tried to browse into both urls, and after key-in administrator with password, a permission error was presented.

Please advise how to solve the problem
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MichaelBalackSenior System EngineerAsked:
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MichaelBalackSenior System EngineerAuthor Commented:
Sorry, the folder is not called "sync error", rather, it is named "sync issues".
stergiumCommented:
Hello.
I would suggest following the official microsoft support steps on that.
http://support.microsoft.com/kb/939765 

Internet options-> connection -> lan settings and check bypass proxy for local addresses and then click on advanced. Type in the ip of your exchange server and click ok. restart outlook. please feed back .
Hope that helps

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chrismkingCommented:
We had the same issues but after upgrading to Exchange 2010 SP3 they were gone.
We also performed the same steps as mentioned above in the Expert Comment.
Good luck!
MichaelBalackSenior System EngineerAuthor Commented:
It works
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