Search in a shared mailbox still problematic

Copper Contributor

We're a small company with 4 users where a shared mailbox is very important for all our work. This includes searching this mailbox to quickly find the right mail(s).


It must be a client issue, because search is working perfectly on the webmail in the shared mailbox.


We have tried everything. Well over 50 threads and guides has been read and followed without any solution (including "Troubleshooting Outlook search issues" of course)


Probably forgot some actions, but from the top of my head these actions have been tried:


  • Add the shared mailbox as separate account. Both as M365 type and Exchange type. This will result in an additional .ost file (2gb+) in the AppData folder.
  • Different combinations of the account settings and HOW to add the additional mailbox ("open additional mailbox" in the advanced tab or not (gets added automatically in some cases)).
  • Closing the mailbox manually by right click from within outlook in the case it was auto-added on start), Marking "download shared folders" nor not.
  • Debugging Windows Search and the indexing operations. Including rebuilding the index (and also changing special indexing options for specific files/types). When choosing the program "Outlook" as object to index about 50,000 things were indexed, but still wasn't searchable in Outlook.
  • All the different cache options (from disabled to 3 months)
  • Increase the time that Outlook waits for Exchange to provide search results before falling back to use local search (ServerAssistedSearchTimeout)
  • All the combination of where to search (click inbox or the whole post box in left pane, and the scope "all outlook objects", "current postbox", "current folder" etc)
  • Completely wiped the profile from Control Panel->Mail and created a new one, with a new account and going with all the default options. Nope.

In some scenarios, the shared mailbox is added with its name visible (e.g. Support). In others, the email address is shown instead (e.g. Not sure which should be "correct".


In some scenarios, the search animation just keeps circling forever. Unsure if something is trying to search at all. In other scenarios, the search just returns "No results" or similar. Sometimes a clickable link below ("More on server" i think) doesn't work either.


On one of our computers, the current status is that search results are shown from SENT ITEMS only, regardless of on which mailbox is clicked, or scope chosen for the search.


This whole thing has now taken such time to debug and gather information about to try to solve it, that we are seriously considering switching to a completely different e-mail solution.


Now we have a completely new computer (W10) with latest Outlook Version 2108 (Build 14326.20404). Is there a detailed step-by-step guide to follow to get search working properly in a shared mailbox? Like, every single step and every single option to follow it 100% ? Nothing is done on this except installed office.


Any help greatly appreciated, but I think only a software update fix can properly solve this.

1 Reply


We've ran into the same issue at our organization. Unfortunately, we've tried all of the same actions as you without luck. We have a workaround in place that is a recommended "temporary" solution per Microsoft. It essentially disables FAST (Exchange online) search and tells the Outlook client to search local cache rather than look to the server. We've implemented it with users experiencing the search issue, and after a reboot, search is restored. 


  1. In Windows, right-click Start, and then select Run. In the Open: box type regedit, and then click OK. This will open the registry editor.

  2. In the registry editor dialog box, find this subkey in the registry, and then click it:

    • HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Search

  3. Click Edit > New > DWORD Value.

  4. Type DisableServerAssistedSearch for the name of the DWORD, and then press Enter.

  5. Right-click DisableServerAssistedSearch, and then click Modify.

  6. In the Value data box, type 1 to enable the registry entry, and then click OK.

  7. Close the registry editor, and then restart Windows.

Hope that helps until a permanent solution is released.