This fragment has worked in many scripts:

#       Save a copy of the email in the temp directory
cat - > /tmp/mailup$$

But this fragment:

FFF="/tmp/arialmailup$$"
cat - > $FFF

generates this:

bronze@ /8 /usr/local/bin ! >cat arialfacecheck  | arialfacecheck
stty: standard input: Invalid argument

FFF="/tmp/arialmailup$$"
++ FFF=/tmp/arialmailup10021
cat - > $FFF
++ cat -