You do not have the permission to send the message on behalf of the specified user.

I have migrated from SBS2008/Exchange 2007 to Office 365.  Everything went smoothly except for the issue below.

I have given user 2 full access to user 1 mailbox and calendar
When user 2 makes a change to a calendar event (created by user 1) and tries to update all the invitees, user 2 gets the following error.

This message could not be sent. Try sending the message again later, or contact your network administrator. You do not have the permission to send the message on behalf of the specified user. Error is [0x80070005-0x0004dc-0x000524]

This does not happen for new calendar events created after the migration to Office 365, only for calendar events migrated before Office 365.

Does anyone have any idea how we can fix this?
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FOXActive Directory/Exchange EngineerCommented:
In the user's outlook that is receiving this error try start > run
Outlook.exe /cleanserverrules
Vasil Michev (MVP)Commented:
When you import the calendar entries, they are created with a different GUID, and thus updating them causes Outlook to 'detect' an issue. You can try updating the organizer of the meeting, which probably will not be possible, so the best option is to just recreate the events.

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ptsolutionsincAuthor Commented:
Nothing we tried worked and decided to not waste any more time troubleshooting.  It was just easier to recreate the events. as Vasil suggested.
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