I have been asked by a company to configure my SPF record (presumably done through my mail host site i.e. names.co.uk) to allow their domain the ability to send-as on one of our mailboxes. Their request appears to grant them the ability to send-as on any of our mailboxes, is this the case? I am not sure how they can only have access to that particular e-mail address e.g. firstname.lastname@example.org.