EWS Basics Accessing and using Shared mailboxes
gsexdev.blogspot.com › 2016 › 10Oct 05, 2016 · Sending Email As a Shared Mailbox To send a message as another user you need to first have either SendAS permissions to that Mailbox or Send on Behalf off (the latter will mean the message will be marked as Sent On Behalf) The first thing in you code you want to do is bind to the SentItems folder of the Mailbox you want to send as eg