Watch this video to see how you can check your email via the web.
Normally you just go to SeaburyHall.org and on the left side you will see a link for WebMail.
Your username must include the "@seaburyhall.org"
You can use this web client to check your email from anywhere, on any computer, as long as you have web access and a browser.
I created this tutorial video with Freez Screen Video Capture. Not sure if I like it, but let me know what you think of the video quality, and if it made sense.