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Based on your description, it seems that there is confusion on the part of the agent receiving the mail. Check the settings from the following perspectives:
- Check the proxy settings to see if the two users who received the wrong email also have a proxy relationship.
- Check if there is a calendar sharing or authorization setting.
- Check your email settings to make sure your calendar invitation notifications are set up correctly. It could be a setting that is causing the difference.
- Check if there are any Outlook rules that affect the way the meeting invitation is displayed.
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