The message was sent to a distribution group that doesn't allow messages from senders that are outside your organization. ...

The message was sent to a distribution group that doesn't allow messages from senders that are outside your organization.

Group name: {Recipient}

To fix this issue, you can change the delivery management setting for the group.
  1. Go to Groups.
  2. Choose the group you want to check, and choose Edit.
  3. Go to delivery management, and choose Senders inside and outside my organization
  4. Choose Save