Gmail

This is probably knocking down an open door, but I have to mention Gmail. I have been using Gmail for several years, and I think it is the best free email available. The available storage is huge (more than 6.5 Gb at this point), and it constantly increases. Pair this with a very good web interface, excellent search abilities (this is Google, remember!) and very good labeling features, and you get a superb email service. Another important aspect is the support for third party applications to read your email. Gmail provides both POP3 and IMAP support, which gives good flexibility. Personally, I love the IMAP support, since it gives me the possibility to store all email on Gmail instead of downloading the email to my local computer.

http://gmail.com