Questions below refer to the following letter.
The functioning of our society is based largely on reliable, convenient and fast (1)............... of exchanging messages. This means that automation in companies must systemize not only data processing, but also data communication. One important step towards office automation was the introduction of electronic mail. This has been in use for a long time, largely in and between universities, but also as an internal means of communication within large companies.
(2)..............., several companies offer this service to their subscribers, in the form of electronic mail-boxes. In the early 80's, it became clear that a significant use of electronic mail could only be possible with international standardization. In particular, general communication between companies is only possible if standardized protocols define the communication between computers from different manufacturers over a (3)............... of transmission media.