At the risk of contributing toward what appears to be the beginning of
a fine flame fest:
a) I side with the privacy folks.
b) I realize that the company can control its resources as it sees fit.
c) You would be well-advised to notify your users that this is happening,
as otherwise you're leaving yourself wide-open to a big lawsuit. There
may be some risk of 'outside' folks getting pissed and filing suit as well.
d) What you want can be cooked-up in Perl (if you like Perl), or awk
in 30 minutes or less, using the sendmail log file (via syslog).