Modern mail is organized by national and privatized services, which are reciprocally interconnected by international regulations, organizations and international agreements. Paper letters and parcels can be sent to almost any country in the world relatively easily and cheaply.
The Internet has made the process of sending letter-like messages nearly instantaneous, and in many cases and situations correspondents use electronic mail where previously they would have used letters. The volume of paper mail sent through the U.S. Postal Service has declined by more than 15% since its peak at 213 billion pieces per annum in 2006.