There used to be a monthly magazine called Rendezvous. You sent off a Polaroid and a postal order, and 2 months later you got a letter from someone who lived 100 miles away. It was VERY hard work!
In practice, of course, it was much easier to shag the woman in the post room, the mucky barmaid, neighbour's missus, wife's best friend, etc. With all the complications THAT entailed.
I think the interweb has probably saved more marriages than it bust up.
**** Oops sorry, should have been a reply to post below.