Does every MBP respect DMARC the same way?

No, not every MBP respects DMARC the same way. While major providers generally honor DMARC policies, smaller providers and corporate systems may implement differently, with some more strict and others more lenient than your policy specifies.

Some providers reject all DMARC failing messages regardless of your policy. Others may quarantine when you specify reject, or deliver despite quarantine policy. Enterprise security systems often have their own rules that override DMARC specifications.

Test delivery to important segments before tightening DMARC policies. What passes at major providers might fail at regional ones or corporate firewalls. Aggregate reports help identify providers with unexpected DMARC handling.