User reported that when he is trying to send email to a DL on behalf on another user (his boss), he gets the following NDR error
This message could not be sent. Error is [0x80070005-00000000-00000000].

Actions Performed

Validated by sending the message a couple of times, but we still get the same message
Tried to send an email to myself from his outlook but on behalf of the boss, still the same error
So we have validated the error is only when he is trying to send as boss
looks like a delegation issue
Checked his permission on his Boss mailbox, found he has no permission
For checking permission , I connected to Office 365 Powershell and executed the following command
Get-mailboxpermission -identity Malissa (this is boss name)
Went ahead and provided him delegation rights again to the Boss mailbox
Issue seems to be resolved


Delegation permission missing, re-added the delegation permission

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An automobile enthusiast at heart and computer geek by profession, started my Career with MS in 2005.Left Jobs and started Pledge Technologies (the parent company to Grishbi) back in 2009.We have been providing IT consulting to various Small and Medium businesses across US and UK since then.Our company specialises in Microsoft Server technologies like AD, Exchange, the rest and with numerous Office 365 migrations under our belt, we quite an expert with that too. Whatever we learn in our day to day life, we share it back on Grishbi as a Thank for all the love and support our customers have given us.