If you use elm to read email go into the directory .elm
and look for a file 'elmrc'. If that file doesn't exist 
you have to create it and add the following line:

# how to print a message ('%s' is the filename)
print = mp %s | lw -ps


If you already have a file 'elmrc' search for the line:
# how to print a message ('%s' is the filename)

and change line
print = mp %s | lw -ps
to
print = /usr/lib/lp/postscript/postprint %s | lp
or
print = /usr/lib/lp/postscript/postprint %s | lp -dchase-mailroom