Monitoring emails sent and received using outlook?

Can anyone let me into a little secret.

If we are on a network in work. And I am using Outlook Express, how is it possible for employers to view the emails I have sent and received?

What form of monitoring could actually do this.

Another issue I have is that I cannot either access, hotmail.com, a message appears like so:

Web Site Blocked By NETGEAR Firewall

The same with any external email client.

If anyone knows please fill me in.

Kind Regards

TS