Distribution list with external email sent from outside

Solution 1:

This is an easy fix.

Think about the reason for this default. Many organizations do NOT want their internal email distribution groups to be presented to the world. Imagine an outside person sending an email to [email protected]. But other times, there are a few addresses that do need the ability to receive email from the outside.

Common examples are: [email protected] or [email protected] - That's where the following settings come in handy:

Navigate to the distribution group's properties under Recipient Configuration in the Exchange Management Console...

Open Mail Flow Settings -> Message Delivery Restrictions.

Uncheck "Require that all senders are authenticated" - Save and exit.