When using a transport rule similar to Opensense's, it is a known issue that when emailing into Offcie 365 Groups a DNR can be triggered. This is a known issue with Office 365. To prevent a DNR when emailing into Office 365 Groups from an internal sender, there are 2 options:
Option 1. Allow External Senders- This option will resolve the issue, but is understandably not super desirable.
Option 2. Create Exclusion Rule for Internal Senders emailing to Office365 Groups. Follow these steps to prevent DNR from occurring. Keep in mind, this will prevent signatures from being processed on these particular messages.
This rule will prevent the Opensense rule for applying on emails sent from internal senders to Office 365 groups, thereby eliminating the DNR issue.
As always, if you have any questions or concerns, please contact firstname.lastname@example.org