There is a known issue on a few limitations when emails are received by a mailbox that is part of a DL, the following functionalities do not work as expected:

1. Case emails will not be created.

2. Corresponding case will not be reactivated.

3. Auto sharing of email will not happen, when the received email sent from the parent case. 

Can this be added to the list if not already discussed with the MSFT Engineering Team .Thanks