Update 4/23/2024: We have now released April 2024 Hotfix Updates which address known issues in March 2024 SU updates.
Microsoft has released Security Updates (SUs) for vulnerabilities found in:
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Updated Apr 23, 2024
Version 8.0
Blog Post
I too am experiencing the issue where users cannot use Search in Outlook clients organization wide.
We have Download Domains activated, but hardly use OWA, most users use Outlook 2019 or 2021 LTSC clients, so the bug was acceptable.
We're running a two server setup in DAG, Server 2022 + Exchange 2019 CU14, both with this update installed today. Problem started as soon as the update went through.
When users search they get "We're having trouble fetching results from the server... " and gives the user the option "Let's look on your computer instead".
Also, not sure if related, but certain internal users, emails from them in Outlook clients also had Icons appearing next to emails received in. This was not happening before the March 2024 SU. It seems to be limited to internal company / domain users only, and only when sent from a client that has restarted their Outlook client since the March 2024 SU was applied. External or Anonymous authenticated users/inbound mail are not affected.