a communication consisting solely of advertising, marketing or publicity material and comprising an identical message, except for the addressee's name, address and identifying number as well as other modifications which do not alter the nature of the message, which is sent to a significant number of addressees, to be conveyed and delivered at the address indicated by the sender on the item itself or on its wrapping. The national regulatory authority shall interpret the term 'significant number of addressees` within each Member State and shall publish an appropriate definition. Bills, invoices, financial statements and other non-identical messages shall not be regarded as direct mail. A communication combining direct mail with other items within the same wrapping shall not be regarded as direct mail. Direct mail shall include cross-border as well as domestic direct mail