Some Exchange Server customers are reporting errors on their Client Access servers after they apply SP2 Update Rollup 3, which was released on May 29th.

The Application event log on Client Access servers begins repeatedly logging Event ID 1 with source MSExchange Autodiscover and the description:

Unhandled Exception: “User setting ‘PreferredSite’ is not available”

As alarming as the error may seem, fortunately it is harmless. Michael Van Horenbeeck spotted this reference to it in Scott Schnoll’s TechEd North America session Microsoft Exchange Server 2010 SP2 Tips & Tricks.

Unhandled Exception: User setting 'PreferredSite' is not available
Unhandled Exception: User setting ‘PreferredSite’ is not available

I listened to the session and Scott confirms it is a harmless code bug.

Given the low impact of the issue it is likely we’ll see an interim update soon for those customers who are experiencing the error, and a fix in one of the next update rollups.

Although harmless (aside from possibly giving admins a scare, and flooding event log-based monitoring systems), this incident once again draws attention to not only the quality of update rollup releases, but also the dissemination of information about known issues after an update is released.

Consider this timeline:

  • 29/05/2012 – Exchange Server 2010 SP2 UR3 released
  • 11/06/2012 – Scott Schnoll mentions the bug in his TechEd presentation
  • 13/06/2012 – Greg Taylor confirms in comments on the release post that it is a known issue
  • 26/06/2012 – Customers are still deploying the update unaware of the known issue
  • 4/07/2012 – The release post, description, and download page still contain no note alerting customers to the issue, and so customers continue to post concerned comments.

Unfortunately not all customers read the various Exchange Server blogs and forums, and will rely on the official release posts and description pages for any known issues. When they do come to the blogs and forums it is after they’ve encountered a problem.

I imagine Microsoft has a content management system that makes speedy updates to some of those pages near impossible. This is probably a good use for a wiki, which exists already on TechNet, but hasn’t to my knowledge been used for publicly and centrally tracking reports of customer issues when deploying service packs and updates.

It could work, but would need to be prominently linked to from the release post and download pages to draw customer attention to it before they proceed with their updates, which could help those customers avoid known issues.

Perhaps something for Microsoft to consider.

About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for


  1. Kyle

    I can also confirm that SP3 with UR2 produces this error. The odd part is that it’s only doing it on one of our CAS servers so far as I can tell, but it’s flooding the event logs and was not doing so on SP2 UR3. All CAS servers have the same config as they are behind a HLB and need to be the same, so it’s odd that only one is doing it. It appears to do it on reboot of the server, and I can “fix” it by performing an IISRESET until the next time it’s rebooted. Any ideas?

  2. Ray Frangie

    Does anyone know if this PreferredSite issue has been fixed?

    Just installed SP3 and we’re still getting flooded with it (then again, I never noticed it in the first place)


  3. Bill Smyth

    Is there any way to resolve this other than an update?

    I tried to apply UR5-v2 for Exchange 2010 SP2 to my two CAS servers, then onto the two DAG servers. After the CAS servers were updated, clients were unable to access with Outlook. WebMail worked OK though. A lack of time prevented much diagnosis, so I backed it out and returned to a base SP2. All is good except now I get this error. Some change was left behind. The domain and Exchange server are new, not migrated, never had Exchange 2003. All less than a year old.

    I need to apply RU4-v2 this weekend to fix this issue for some users:
    KB 2632409 Sent item is copied to the Sent Items folder of the wrong mailbox in an Exchange Server 2010 environment when a user is granted the Send As permission. That will not resolve this error though.

    I see RU 6 came out. Normally I would have gone with the latest to get the security updates, but my confidence in the RU’s is not what it use to be. Maybe in a few months after the dust settles or just wait for SP3 to be proven. Hopefully Microsoft gets their quality control back.

  4. Shawn

    We just did a new install of Exchange 2010 with SP1 and then applied SP2 and the Windows Update Roll Up 4 V2. The error is still present. Any further word on whether Microsoft addressed this in a roll up?

  5. Klaus

    Not enough fingers crossed.
    RU5 seems to be another FAIL.

  6. Nitin

    yep , error still there after applying the recently released will have to wait further.

  7. Jeff

    It doesn’t look like UR4 fixes this either.

    1. Avatar photo
      Paul Cunningham

      Probably not enough time to get it through QA before UR4 was released. Fingers crossed for UR5 🙂

  8. Ed


    i was one of the Inpatient people who applied SP2 RU3 and started getting the error, Logged a call with MS and just early this week they sent me a hot-fix for it.

    1. Avatar photo
      Paul Cunningham

      Thanks for letting us know Ed. Did they give you a URL where the KB can be requested or only via phone?

      1. Ed

        Hey Paul,

        no, they didn’t send me a download link. it was emailed to me.

        i’m happy to fwd to you and you can make it available for everyone.

        1. Avatar photo
          Paul Cunningham

          Thats okay, I wouldn’t host a hotfix. People should only get those directly from Microsoft 🙂

          I’ll see about chasing up a URL but my guess is if they are giving it out on support calls it will probably be in one of the next update rollups anyway.

  9. Chris Saint

    If you can, stay away from UR3, it breaks some stuff.

  10. Shane Bryan

    We’re about to apply this UR for our environment tomorrow. So glad I found this article.

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