Virtualization, Cloud, Infrastructure and all that stuff in-between

My ramblings on the stuff that holds it all together

OWA 503 Service Unavailable following 973917 update


I’ve seen a couple of instances of this in the last week where previously working Exchange 2003 servers suddenly stop serving Outlook Web Access (OWA) Requests overnight

Investigating the eventlog shows the following entry which corresponds with stopped application pools in IIS Manager;

Event Type:        Error

Event Source:    W3SVC

Event Category:                None

Event ID:              1059

Date:                     14/12/2009

Time:                    02:01:37

User:                     N/A

Computer:          EXCHANGESERVER


A failure was encountered while launching the process serving application pool ‘DefaultAppPool’. The application pool has been disabled.

For more information, see Help and Support Center at

This seems to be related to a recent Microsoft Update – 973917 uninstalling the hotfix, followed by a reboot immediately resolves the problem and OWA starts working again.

I’ve also had reports from people that this update has affected some other bespoke IIS applications, again uninstalling the patch seems to resolve the problem.

This situation seems to arise from a mismatch of installed binaries – now I thought system file protection and the .msi based patch installers were supposed to avoid this situation from Windows 2003 and onwards – anyway for more information on the cause and how to resolve without uninstalling the 973917 patch see the following links

One response to “OWA 503 Service Unavailable following 973917 update

  1. galan June 8, 2010 at 3:09 am

    I come accross this misery events three times and i solved:
    First Case#1: Interface IP configuration problem.
    Look your local driver E:\Windows\System32\drivers\etc\host
    If you see any entry like this:
    fe80::9069:9334:813e:868 ComputerName # Added by Office SharePoint Server Search (6/8/2010 4:45 AM). It means office sharepoint server is removing your ip 4 entry.
    Then you have problem of IP 4 & 6 conflicts so to solve it disactivate the IP V6 of your interface and remove the entry and run IISRESET. The problem has gone.

    Second case #2: Exchange server version 2003 problem.
    Administrative tools->IIS->Default website->properties->ASP.Net choose version 2.0.
    Run IIS RESET and the problem is gone.

    Case #3: Exchange server version 2007 problem.
    isapifiler for exchange when bad request arrives. change precondition to 32 or 64
    IIS configuration sections

    i hope one of this will solve ur problem.thanks

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