I needed a user (UserB) to "send on behalf" of another user (UserA), and also see all of the user's folders in their mailbox.
I gradually added permissions and delegation.
I started with adding UserB as a delegate. I could send on behalf, but only see the Inbox and Calendar - none of UserA's other mail folders.
In order to see the Full mailbox contents, I added Full Mailbox Access via the Exchange Advanced tab in AD, and also had Send As/Receive As on the Security tab. Now, when UserB sends from UserA, it does not show as "on behalf of UserA" at the recipient.
I've removed the permissions in the same order I added them, and I can't get back to "sent on behalf" and still see all the mail fodlers.
What are the correct settings for Delegation and Mailbox permissions to see the entire mailbox and still send "on behalf of"?