Answer:

During the 1700s, before the invention of postage stamps, the receiver of the letter was responsible for paying the postage fee. This system was known as the "receiver pays" model, and it was the prevailing practice in the postal systems of many countries at the time.

Explanation:

1. The "Receiver Pays" Model:
In the absence of postage stamps, the postal service relied on the "receiver pays" model, where the person who received the letter was required to pay the postage fee. This meant that the recipient had to pay for the delivery of the letter upon receiving it. The fee was usually collected by the postal carrier at the time of delivery.

2. Reasons for the "Receiver Pays" Model:
There were several reasons behind the implementation of the "receiver pays" model:

- Accountability: By making the receiver responsible for paying the postage fee, it ensured that the postal service was compensated for its services. It held the recipient accountable for the cost of sending the letter.

- Lack of Prepayment Options: At that time, there were no postage stamps or other prepayment options available. The sender had no means to indicate that the postage fee had been paid.

- Variable Postage Rates: Postage rates were often determined by the distance the letter had to travel, the weight of the letter, and the number of sheets of paper used. Calculating these rates in advance would have been impractical for the sender.

- Limited Postal Services: The postal service in the 1700s was not as well-developed as it is today. The "receiver pays" model was a way to ensure that the postal service could sustain itself financially.

3. Evolution of Postage Stamps:
The concept of postage stamps emerged in the early 19th century as a way to simplify the payment process and alleviate the burden on recipients. The first adhesive postage stamp, the Penny Black, was introduced in the United Kingdom in 1840. With the introduction of postage stamps, the sender could prepay the postage fee by affixing a stamp to the letter, eliminating the need for the receiver to pay.

Conclusion:
In summary, in the 1700s, the receiver of the letter was responsible for paying the postage fee before the invention of postage stamps. The "receiver pays" model was implemented as a means of ensuring accountability and sustaining the postal service. The introduction of postage stamps in the 19th century brought about a significant change in the payment process, allowing the sender to prepay the fee and simplifying the system for both parties involved.