Hi Sagima,
If you open the distribution group properties, you can select approved senders under the 'delivery management' tab. You will be able to select individual users and groups.
We use Veeam Endpoint for our physical servers now. It's free and you can backup to your Veeam Repository! It isn't purposely built for server use, but it still works well.
Veeam Endpoint Backup Free for desktops and laptops