Microsoft Outlook: “We’re having trouble fetching results from the server. Some items may not be included in your search results.” after Exchange 2016 / 2019 update

When searching with Outlook you might end up with warning message: “We’re having trouble fetching results from the server. Some items may not be included in your search results.” For us this happened after running Windows update which applied some updates to Exchange.

The reason for this seems to be that the Outlook search returns less items than expected and some items may appear to be missing. This issue is mostly a client side issue but for us it seemed to be related to Exchange update. To fix the problem, check the following:

• Can you search with OWA (Outlook Web Access aka Webmail)?
  • If yes, this is usually client side issue
    • Your Microsoft Outlook is up-to-date with updates
    • Try rebuilding Outlook Search Index (File – Options – Search – Indexing Options… => Select Microsoft Outlook => Advanced => Rebuild)
    • Use Cached Exchange Mode with sync option All (File – Account Settings – Account Settings => Select your account => Change => Select “All” => Next – Finnish)
    • Try creating a new Outlook profile (Control Panel – Mail – Show profiles… – Add… => Give name and your email account details => Remember to change the default profile to the new one)
  • If not, this this server side issue
    • Update your Exchange to the latest CU (Cumulative Update)
    • Update your Exchange after the latest CU with Windows Update
    • Try disabling and re-enabling Full text indexing:
      • Get-MailboxDatabase | Set-MailboxDatabase -IndexEnabled $false
      • Get-MailboxDatabase | Set-MailboxDatabase -IndexEnabled $true