Network/User monitor

I am looking of software that can do the following:

Email monitoring:

Should be able to scan for certain words
Attachment/email size.

Internet traffic usage:

The software should be able to track the amount of Data the user downloads/Sends via the internet. (If it logs the sites so much the better)

It should work with Linux Suse 9 with Post fix, Linux Suse 10 with Groupwise.

The workstations are all Windows PCs nubering in the 800s

Thanx