I'm looking into giving a Multi Tenent mailbox user Full Mailbox and SendAs rights to another mailbox in the same domain. I have managed to adapt the SendAs command as below:
Get-mailbox -Organization "Org" -Identity "User" | Add-RecipientPermission -AccessRights SendAs -Trustee "Admin user"
I'm getting errors when trying a similar command for the FullAcess.
There is no info on this on the Multi-Tenent part of the TechNet Library.