Hello,
Popular monitoring software such as
NetNanny is good for monitoring a lot of other communications, but unfortunately it can not monitor email.
Are you able to send and freeze their outgoing mail server settings?
Are they only using programs on their computer to send mail?
Do they have access to and could they also be sending from free webmail such as Yahoo Mail?
You could try a business email hosting package that includes email archiving and force their mail program to send email through those servers.
There are lots of ways to send email, and there are plenty of ways to get around 25/tcp, the port generally used for sending email.
The best bang for your dollar could be something like this
keystroke logger from Amazon.
It won't let you approve emails before they send, but at least you'll see what was typed.
to Email Questions!