In the Exchange application log you observe:

The Module DLL C:\Windows\system32\something\whatever.dll failed to load. The data is the error.

Followed by:

Could not load all ISAPI filters  Therefore site 'DEFAULT WEB SITE' startup aborted

Fix:

On the application pool for the site click on advanced settings:

Exchange Blog_dll_1

Then change the setting pertaining to support for 32-bit applications.

Exchange Blog_dll_2

Then a bunch of other dll files are going to start throwing errors one by one. You must perform the following procedure for each:

in this example the error is thrown by kerbauth.dll and reads as follows...

Module DLL 'C:\Program Files\Microsoft\Exchange Server\V14\Bin\kerbauth.dll' could not be loaded due to a configuration problem. The current configuration only supports loading images built for a x86 processor architecture. The data field contains the error number

1) in the file "applicationHost.config" located at:

C:\Windows\System32\inetsrv\config (SAVE A COPY OF ORIGINAL SO YOU CAN REVERT BACK QUICKLY)

2) add this line to the area indicated below by using find: preCondition="bitness64"

Example in my case: This is BEFORE CHANGE:

add image="C:\Program Files\Microsoft\Exchange Server\V14\Bin\kerbauth.dll" name="kerbauth"

And this is after the change, when we add the line as described above:

add image="C:\Program Files\Microsoft\Exchange Server\V14\Bin\kerbauth.dll" name="kerbauth" preCondition="bitness64"

  • restart app pool or iis
  • keep returning to the application log in the event viewer to see what dll is unhappy next, perform until red errors related to dll files stop
  • KEEP TRACK OF WHAT YOU CHANGE

Possible step 3)

3) If a dll like owaauth.dll throws the error you must add the preCondition ="bitness64" to the following area

filter enabled="true" name="Exchange OWA Cookie Authentication ISAPI Filter" path="C:Program FilesMicrosoftExchange ServerClientAccessowaauthowaauth.dll" span="span" preCondition="bitness64"/

4) then just start the AppPool again and 32 bit application will now work just fine.. and our AppPool wil not be stopped again....