http://www.mailart.be/initiation.html . The second article is entitled "Mail-Art During This Last Decade". "In the end," Bleus says, "not the computer, fax-machine or postbox, but communication is the message".
There is the third essay in the book by Silvia Topa Marazzina unfortunately in Italian that is totally Greek to me.
The catalog is of size 22x14.5 cm and has 90 color pages.
Many thanks Bruno!
See their projects brochure also.