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* Coping when the host-name passed to ``lookup_receiver_policy``
for hosts that start with ``_dmarc`` already
* Rejecting all answers that do not start with ``v=DMARC1``, as
per `Section 7.1`_ (number 5) of the draft DMARC specification
.. _Section 7.1: https://tools.ietf.org/html/rfc7489section-7.1