If you want to set up a Distribuition group to receive emails from external email addresses.
Open Exchange Management Console.
Navigate to Recipient Configuration>Distribution Group and then right click the distribution group that needs to receive external emails, and go to properties.
Mail Flow Settings tab>Message Delivery Restrictions>Properties, uncheck “Require that all senders are authenticated”, and click OK
![](https://i0.wp.com/static.spiceworks.com/images/how_to_steps/0003/5188/288984a27b782dce84e5e8ef2ddb4f90b23d8d2d2bc6c55aea022bd71f1758cd_dg_settings.png?w=980)