Outlook Indexing option grayed out

It is possible that the Modify option is grayed out because the Indexing status is not yet complete or still loading. Let us try to wait up until it is finish and completed to check if the Modify option will be available. If still the same, lets try the below steps:

1. Allow indexed option from OST

• Go to “File” > “Account Settings” > Again “Account Settings“.
• Choose the “Data Files” tab.
• Write down the “Location” for “OST” file. Then go to the folder specified.
• Close your Outlook.
• Using “Windows Explorer” go to the folder where the OST files are These are the folders you wrote down in the location section. Basically, the location is usually“C:\Users\yourusername\AppData\Local\Microsoft\Outlook“.
• Then highlight all the OST files in the folder. (Hold the “CTRL” button to click and select all).
• Do a Right-click on the highlighted file, then select “Properties“.
• Then Select the “Advanced…” button.
• Do Check the “Allow this file to have contents indexed in addition to File properties” option if it isn’t checked previously, then go to “OK“.
• Now Open your Outlook, then go back to “File” location >then “Options” > “Search” > “Indexing Options” > Click on “Modify” and recheck “Outlook“.

2. Rebuild your search catalog.

• Close Outlook and open Control Panel. Depending on the version of Office you're using, you might need to click the Start button, and on the Start menu, right-click Control Panel.
• Do one of the following:
  a. Choose Indexing Options.
•           b. In the Search box, type Indexing, and then choose Indexing Options.
• In the Indexed Locations dialog box, under Change selected locations, select the check box for the location you want to modify, and then click OK.
• In the Advanced Options dialog box, on the Index Settings tab, under Troubleshooting, click Rebuild. A Rebuild Index dialog box opens warning that the "index might take a long time to complete." Choose OK to start rebuilding the index.

3. Registry Edit 

Create a new DWORD (32-bit), name it PreventIndexingOutlook and give it a value 0.

Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Windows Search

4. Check Group policy setting 

• You also have a look at at the Group Policy settings and make a slight change if needed.
• Run gpedit.msc to open the Local Group Policy Editor and navigate to the following setting:
• Computer Configuration > Administrative Templates > Windows Components > Search
• In the right side, you will see Prevent indexing Microsoft Office Outlook. Ensure that it is set to Not Configured or Disabled.

6. Windows Search service is still running

Press Win key + R to open the Run command, type services.msc and press Enter. Check whether the status of Windows Search is Running. If it is stopped, try starting it. If it's already running, try stopping it and then starting it again to see the result.

For any other concerns related to Office 365 plan and subscriptions. You can reach out to us by submitting a ticket on our portal https://cloud.foetron.com/. Check out our website www.foetron.com to know about the services offered by us.