def __check_msg_for_headers(self, msg, ** email_headers):
        """
        Checks an Email.Message object for the headers in email_headers.

        Following are acceptable header names: ['Delivered-To',
            'Received', 'Return-Path', 'Received-SPF',
            'Authentication-Results', 'DKIM-Signature',
            'DomainKey-Signature', 'From', 'To', 'Message-ID',
            'Subject', 'MIME-Version', 'Content-Type', 'Date',
            'X-Sendgrid-EID', 'Sender'].

        @Params
        msg - the Email.message object to check
        email_headers - list of headers to check against
        @Returns
        Boolean whether all the headers were found
        """
        all_headers_found = False
        email_headers['Delivered-To'] = email_headers['To']
        email_headers.pop('To')
        all_headers_found = all(k in msg.keys() for k in email_headers)

        return all_headers_found
Checks an Email.Message object for the headers in email_headers.

        Following are acceptable header names: ['Delivered-To',
            'Received', 'Return-Path', 'Received-SPF',
            'Authentication-Results', 'DKIM-Signature',
            'DomainKey-Signature', 'From', 'To', 'Message-ID',
            'Subject', 'MIME-Version', 'Content-Type', 'Date',
            'X-Sendgrid-EID', 'Sender'].

        @Params
        msg - the Email.message object to check
        email_headers - list of headers to check against
        @Returns
        Boolean whether all the headers were found