I need to add "Send As" permissions for a shared mailbox in Exchange 2013, however I need to grant it on an AD Group.
I've already added FullAcceess to the group via powershell and the command for adding the group to "Send As" works too, but some time after setting the permission it reverts to not set.
This is the command I used:
`Get-Mailbox "name" | Add-ADPermission -User "group" -ExtendedRights "Send As"`

The EAC shows, that the permissions were applied, but like an hour later they are gone. Am I doing something wrong or is it not possible to grant "Send As" to an AD group?