EMail monitoring in the workplace is quite simple. Allow me to break it down:

- The network is owned by the organization one works for. It's their stuff, they can do what they want with it. It's perfectly legal....and ethics don't come in to play. It's business, not personal. Just the way it should be.
- When you're at work, you're selling your time to the company you work for. Therefore, for lack of a better term (trust me), they "own" you for that given period of time.
- 99% of all hardcore email monitoring is done at random...the rest is filters and such to weed out known viruses, etc. If a company really has someone sitting there reading all of the emails, then that's their own fault for being un-intelligent and wasting money.
- Security. Security is a huge reason this is done. It comes in many different forms...anywhere from filtering viruses and junk mail, to monitoring one person's email, as you may suspect them of corporate espionage. (yes, this happens more than you may think).

I'm a net admin...and I do NOT read people's email. There are waaaaay too many other things that I have to keep an eye on. If an executive or manager wants something/someone watched over, it's my professional duty/responsibility to do as asked.

All in all: I have no problem w/ email monitoring. Don't do your personal things at work. You're there to do a job, not to goof around.