CSNET

from The Free On-line Dictionary of Computing (8 July 2008)

CSNET

   Computers and Science Network, operated by {CREN} for US
   computer science institutes.  It provides {electronic mail}
   service via {dial-up} lines, {X.25} and {Internet} services.

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

CSNET
       Computer + Science NETwork (USA, network, BITNET)