Foreign cargo service in thillai nagar International Air Express (courier DHL, Fedex, UPS, blue dart, aramex air cargo and sea cargo) Is The primary function of post office is collection, processing , transmission and delivery of mails. All postal articles whose contents are in the nature of message can be classified as Mails which includes Letters, Postcard, Inland letter card, packets, Ordinary, registered, insured, Value payable articles, speed post.