Hi anonymous user,
We observed that cpu usage can spike to 100% when our event-mailbox sends out Calendar Invitations with multiple distribution-lists and recipients (Over 8000 recipients).
Is this a recently occurred issue? If so, have you made any changes to your Exchange environment before the issue started?
Does it affect meeting invitations sent to less distribution-lists and recipients, like 1000 recipients?
What about sending a normal message rather than a meeting request, will it case the same high CPU usage?
Given current situation, I'd like to suggest having a check via the Event Viewer and see if there would be any relevant events recorded. Besides, have you installed any third party applications like anti-malware on the Exchange server? If yes, it's recommended to temporarily disable them to help narrow down the problem.
Furthermore, the latest build for Exchange 2016 is now CU18, you may consider upgrading to the latest version to see if there would be any improvement.
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