Hi @Alexis Pejouan ，
I wonder if this is a fortuitous event, or a regular occurrence in your team?
Can you find this message in the Sent folder? Please have a check if you have set a delay or schedule send.
At that time she was configuring her iPhone after an iOS update last night.
In addition, we likewise cannot rule out if this is a problem caused by iOS .
Here is a similar case that the meeting invitation automatically sent from the users' mobile devices:Meeting Invite Automatically sent from the user mobile devices without their knowledge. (microsoft.com)
Hope it can help you !
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