Sending out Meeting invite to attendees is nothing new to Outlook users. We have all been there and are fully aware how it works.
However, not everyone is invested when it comes to adding a Delegate to your mailbox and that’s where I come in.
This recently came to my knowledge after a colleague told me that in Office 365, when a delegate is added to a mailbox, and upon trying to Send or Accept a new meeting invite, an email is sent out to the mailbox owner and the From line of the message says “<Delegate> on Behalf of <Mailbox>.”
Two things happened here:
- Email was accepted/sent out, Sure; and the behavior was expected. Subject of that email had <Delegate’s Name>on Behalf of <Mailbox><Email Subject>
- However, another email went out to the mailbox owner(and this is regardless of mailbox owner being kept in loop) informing of the recent activity his mailbox was engaged in by whoever took that action.
What’s the Cause?
I’m glad you asked! When a delegate is added to a resource mailbox through the Select delegates who can accept or decline booking requests option, the delegate is granted “Send on Behalf” permissions. This behavior is by design in Office 365.
How to prevent this?
From Exchange Admin Center, search for the mailbox and double click on it. Select ‘Mailbox Delegation‘, and under Send As, add the delegate.
Important Note: Don’t remove the delegate who is listed under Send on Behalf. Removing the delegate also removes delegate access.
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