One of our clients needs all users with a mailbox to be granted
Full Access and
Send on Behalf permissions to another shared mailbox.
The easiest way to do this would be to give a security group the needed permissions, but Exchange 2013 is only allowing delegates that are users. I've tried via ECP and the following (assuming "sharedemail" is the shared mailbox and "AllUsersSecGroup" is an AD Security Group):
Set-Mailbox -Identity "sharedemail" -GrantSendOnBehalfTo "AllUsersSecGroup"
I can't use
Add-MailboxPermission because there's no operator for
Group instead of