Another method would be creating a Outlook inbox rule in one member mailbox of this distribution list to forward the email sent to this distribution list to the other user.
For detailed information about how to create a rule in Outlook or OWA:
Set up rules in Outlook
Use inbox rules in Outlook on the web
The rule would be like:
If you would like to use Exchange Management Shell, you can use this cmdlet:
New-InboxRule
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