When you create an user or a distribution group which always has no message delivery restriction, you should adjust delivery setting if required. Some distribution groups are created for public usage but some of them are created for limited or private usage.
In this scenario, I have a distribution group which needs to restricted.
Open Microsoft Exchange Server management Console and go to
Microsoft Exchange On-Premises>
and choose your distribution group that you want customize and right click on it and open properties and click Mail Flow Setting
Open Message Delivery Restriction
Choose “Only senders in the following List” and Click Add
After users are chosen, click ok, and again ok
Now, I have a distribution group and only Sonat YAYLALI is able to send an email to