Direct Entry is a term that was first used in the 1980s, when companies began shipping mail intended for a particular country directly to that country (either via air, sea, or land), and then entering the mail into the local postal system for delivery. Postage was paid at the local (domestic) rate, with stamps or postage-paid impressions affixed to the mail.
The combination of freight (air, sea, or land) from the country of origin to the country of destination — plus the cost of domestic postage — was often less than the cost of international postage from the originating country. And because the mail was entered into the local mailstream and properly sorted, delivery and reliability was improved.
Direct Entry is still widely in use. It can provide improved delivery because transit times can be carefully monitored, and because mail is sorted to the requirements of the receiving (foreign) postal administration. (In contrast, mail sent through the international mailstream is not sorted to the requirements of the receiving postal administration.)
For Direct Entry to be cost-efficient, the international mailing company must have substantial volumes of mail for the intended receiving countries.
Direct Entry should not be confused with Direct Injection, which came about later and requires less effort on the part of the international mailing company.