Our environment consists of a single Exchange 2016 CU8 server and multiple clients using Outlook and OWA.

Searching (fast search and advanced find) both are not working in either OWA or Outlook desktop. The results are simply empty with "no items found."

Additional weird symptoms:
MSExchangeFastSearch is throwing the following in Event Viewer:

An operation attempted against a FAST endpoint exprienced an exception. This operation may be retried. Error details: Microsoft.Exchange.Search.Fast.PerformingFastOperationException: An Exception was received during a FAST operation. ---> System.ServiceModel.FaultException: Could not load file or assembly 'Microsoft.Exchange.TransportFlowMdm.105, Version=, Culture=neutral, PublicKeyToken=0fbbedb750799a68' or one of its dependencies. The system cannot find the file specified.

And when checking on the database content status of the newly created DB:

ContentIndexState            : Unknown
ContentIndexErrorMessage     : Could not find registry value of Index Status for database

Steps I've tried:
1) Rebuilding content index (now it shows "healthy"
2) Moving mailboxes to new database

I'll be upgrading to CU9 over the weekend as a last-ditch effort. Anyone have ideas?

3 Answers 3


First, please ensure the Microsoft Exchange Search and Microsoft Exchange Search Host Controller services are running. Then, after rebuilding the content index state of the database, we can wait for some hours to search again and check if any helps. Moreover, please also run the following command to check if the content index state of other databases are healthy:

  • Get-MailboxDatabase |Get-MailboxDatabaseCopyStatus |fl Name,ContentIndexState

If you are still now getting helped, again rebuilt a failed content index by stopping the running search services, such as:

  • MS Exchange Search Host Controller – C:>stop-service HostControllerService
  • MS Exchange Search  – C:>stop–service MSExchangeFastSearch

Note: It is recommended to execute this task outside of business hours as it may cause High CPU Utilization on Servers

Then follow the steps as given below:

  1. Get the location of the Content Index.
  2. The Content Index is located in a folder called GUID of the database.
  3. Now, delete the folder as repeat the steps for every failed content indexes.
  4. Then, start the search service again.
  5. Reconstruction will be done after some time depending upon the amount of data.

This is all about the solution, click here if you want to get detailed step solution.


Here are some steps you can take to fix Outlook and OWA search:

  1. Rebuilding the content index, ensure that the content index state is not only "healthy" but also reflects the correct status for each database. These steps vary for standalone server and DAG. Refer this link.

  2. You can Look for additional error messages or warnings in the Event Viewer related to MSExchangeFastSearch. These might provide more insights into the root cause.

  3. Your plan to upgrade to CU9 is a good step. It often includes bug fixes and improvements that might address the issues you're facing.

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