Google's GMail service is a web-based service. Some people have security concerns based upon the fact that all mail is electronically scanned by Google's software. (The stated reason is so that advertising matter can be accurately targetted at users. However, pro-privacy groups are still concerned about the possible misuse of the system):
http://www.privacyrights.org/ar/GmailLetter.ht m
In my opinion, the best free e-mail service, which is compatible with e-mail clients such as Outlook Express, has to be Gawab. The main pages on the website sing the praises of their web-based access but you never need to use this if you don't want to. (Just consult the link for 'Features > POP/SMTP', at the top of the page, for details of how to set up Outlook Express). The best way to commence the sign-up procedure is to click on 'More cities & countries'. This will offer you a range of domain names. (I use both gawab.com and alex4all.com):
http://www.gawab.com/webfront/main.php
(You can sign up as many times as you like, so you can have multiple e-mail addresses).
Chris