Electronic mail is another PC to PC and PC to mainframe data exchange. If you subscribe to an electronic mail service, it will enable your PC to gain access to a 'mailbox' on a mainframe somewhere. You can either post data to the mailbox for someone else's PC to read later; or your PC can interrogate the mail box to see if anyone has left any data for you.

This system is now widely used for stock ordering, and many of your suppliers will have an electronic mailbox. The most competitive companies equip their salesmen with computers. Once a sale is made, the salesman sends exact I ordering details to his distribution manager's mailbox. The distributor interrogates his mailbox every few hours, and should be able to despatch and invoice the sale within hours.