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. These are classified as first class and second class mails. First class mails get free Air mail transmission within India; whereas second class mails get air lift only if prepaid with air surcharge. These four stages of mail operation have a single aim - Delivery of mail to its addressee.