It is a badly designed attempt to do a forced download and execution of
the file CryptoSMS.EXE on your computer. There is some question whether
it is malware or simply a spam attack. Either way any reasonably secure
computer shouldn't have a problem with it but there are still millions
of people out there who never hear of the word security and they are the
prime target. Do a Google search for the filename and you'll get many
hits but there seems to be little agreement about what is going on.