How to Resolve Owaauth.dll Related Errors and Security Issues

Owaauth.dll is a dynamic link library file created by the Microsoft Corporation and used by Microsoft Exchange OWA Form-Based.

Error Message:

C:\Program Files\Microsoft\Exchange Server\ClientAccess\Owa\auth\owaauth.dll' could not be loaded due to a configuration problem. The current configuration only supports loading images built for a x86 processor architecture.


If you get this error, you have to switch between the 32-bit version of Microsoft ASP.NET 1.1 and both the 32-bit version and the 64-bit version of ASP.NET 2.0 on a 64-bit version of Microsoft Windows. This article from the Microsoft knowledge base will tell you how to switch between both the 32-bit version and the 64-bit version of ASP.NET 2.0 on a 64-bit version of Microsoft Windows.


For forms-based authentication in OWA for Exchange 2003, the following problems may occur:

  • The first letter of the user’s account name is truncated.
  • The domain name is not correctly populated.
  • You cannot change passwords for users whose passwords must be changed at the next logon.
  • You cannot change passwords for users whose passwords have expired.
  • You cannot change passwords across forests.
  • You cannot use user names in the UPN format.

Cause of the Issues:

Issues associated with Change Password pages occur because there are technological limitations of Active Directory Service Interfaces when used in an Active Server Pages (ASP) page on a Web site.


There is an available hotfix from the Microsoft Help and Support page for these issues. Note that there are additional steps to follow after you apply the hotfix. You should configure the Password Change functionality after the hotfix is applied.


Upon providing credentials, the url would redirect to https:///exchweb/bin/auth/owaauth.dll. Internet Explorer would show an HTTP 500 Internal Server Error.

You will see this error when you use Microsoft Outlook Web Access 2003 to connect to your Microsoft Exchange Server 2003 mailbox.


There may be two causes for this particular issue:

  • The Exchange virtual directory is not running in the correct application pool.
  • The ExchangeApplicationPool property has the incorrect identity.


Exadmin, Exchange, Exchweb, Exchweb\Bin, Exchweb\Bin\Auth, Microsoft-Server-ActiveSync, and Public virtual directories must run in the Exchange Application Pool. They should not be in the Default Application Pool. More detailed instructions may be found on the Microsoft Help and Support page.


Owaauth.dll file vulnerability security issue

There is a vulnerability in Microsoft Outlook Web Access that allows malicious individuals to redirect the login to any url they desire. Users will be redirected to the attacker’s site where phishing may be employed.

For the attack to be successful though, you must click on a URL that is appended to the normal company OWA url, get past a security alert message on the browser and re-enter credentials at the malicious site.

There is a workaround that will remove users? capability to provide a redirect URL via the FBA QueryString until the next version of Exchange Server.

Here are the steps for this workaround.

  1. Go to C:\Program Files\Exchsrvr\exchweb\bin\auth\usa
  2. Substitute the locale you are using with usa if using a different one.
  3. Create a backup copy of logon.asp before editing this particular file.
  4. Now go to line 54 of logon.asp.
  5. For Microsoft OWA servers, line 54 should look something like this: redirectPath =
  6. Hardcode the redirectPath variable to the path you are passing in to the URL.
  7. Exit and save logon.asp.

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