Yes, Tourism was a concept developed by H. R. Fricker back in the mid 1980's.
First, he started a project called "Decentralized Exhibition of the Year", or something like that, in wich the works will be held not at one place, but everywhere there where the artist lived. The audience could not see all works at one place, but they had to travel to see the complete exhibition. In 1986. he and Günther Ruch organized the first international MA-Congress and developed the concept of decentralized world-wide mail-art congress, "where two or more people meet, there a congress will take place". Then another congresses took place. It seems that the concept of "congress" (from G. Ruch) separate from the one of "tourism" (from Fricker), but in fact, the two of them are mixed. H. R. Fricker continued developing the concept and a lot of mail artists began to call "tourism" to the fact of travel to visit their correspondents or to meet them in person. The case of Peter & Angela Kustermann was a top in the development of the concept: they travel all around the world through a full year, wearing postal uniforms, visiting their correspondents, carried mail between them and organizing decentralized networking congresses.
