If you send an email from your own account it's possible to fake the apparent address but anyone clicking on 'Properties' will still see where it's come from.
If you set up a new email address with, say, Gawab and then use it to send e-mail relating to (for example) terrorism, the security services in this country would have to get their colleagues in Egypt (where Gawab is based) to serve a court order on Gawab to identify which UK ISP the mail came from. The UK security services would then have to serve a court order on your ISP to get them to identify you. So, as you state, it is possible to 'back-track' emails. However, it can only be done through international cooperation and court orders. (Even then, if you sent the mail from an internet caf�, it would still be very difficult to trace you). As long as your intentions aren't of a nature that would warrant such an investigation, you can use services like Gawab (or Hushmail or Hotmail or Yahoo or thousands of others) with complete anonymity.
Instructions on setting up an account with Gawab are in paragraphs 3 et seq of my post here:
http://www.theanswerbank.co.uk/Technology/Inte rnet/Question407429.html
Chris