Troubleshooting Office 365 email channels
From time to time it is possible you may experience alerts or sending errors related to you Office 365 email channels. Here we explore some of the most common issues and provide some information on how to address them.
Sending access error
Error: Sending on behalf of that Office 365 shared mailbox is denied. Please verify your Office 365 rights.
You may see this error message appear both as a popup and as a banner applied to a message you are attempting to send.
When attempting to send this message via Office 365, Office 365 responded with an error message due to permissions set for that email address.
How do I resolve this?
This is effectively caused by the Office 365 user who authenticated this email channel not having the correct permissions set in Office 365 to send on behalf of that user.
You can take a look at Microsoft's explanation of why you are seeing this error, and what you can do to resolve this error here in the Microsoft Support article - An error may occur when sending On Behalf of or Sending As another user when using the Microsoft Dynamics CRM Email Router with Office 365 Exchange Online.