"course of transmission" means in case of, for a postal article, the time from the delivery of the postal article to the licensed postal service operator until the time of its delivery to the addressee, its return to the sender, or its disposal under the applicable provisions of these Regulations; "definitive stamp issue” means stamps depicting nature or natural heritage and which are valid for a maximum of ten years from the date of issue; "postal services licensee" means the Postal Corporation of Kenya and all organisations licenced to provide unreserved postal services, including courier companies, transporters, freight, forwarders, delivery companies and direct marketing companies which handle postal articles; "reserved postal services" means (a) the collection, transport, sorting, and delivery, for hire or reward of letters and postcards weighing up to 350 grams, but not including exempted letters sent by licensed courier, letters accompanying goods at the time of delivery, newspapers, magazines, books, nonaddressed leaflets, catalogues, and trade announcements letters delivered otherwise than for reward letters delivered by an employee of the sender letters containing any writ or proceeding out of court or any legal instrument of any kind and, letters carried to the premises of a provider of electronic mail service for the purpose of transmission by electronic mail; (b) the production and issuance of postage stamps, pre-stamped envelopes, aerograms, and international reply coupons bearing the official national coat of arms or the words "Republic of Kenya," "Kenya," or "Kenya Post"; and (c) the rental or lease of private letter boxes or bags; 51