Webmail is very common. You log into a site and get your mail. But that is not the same thing as using a program that lets you read and edit your mail while not connected to the internet.
An email program like Thunderbird or Outlook can be set up as POP.
But what about IMAP?
Short for Internet Message Access Protocol, IMAP was developed at Stanford University in 1986 and is a protocol that allows users to retrieve e-mail but still uses SMTP for sending e-mail messages.
http://www.computerhope.com/jargon/i/imap.htm
Fastmail is a company that offers both free and business E meal service. They recommend IMAP for commercial users.
IMAP is a much more advanced protocol that allows you to see all your folders on FastMail.FM, and quickly view subjects and message bodies of emails, but delay downloading of larger emails (such as those with attachments) to a later time if you want. IMAP also allows you to synchronise mail folders between your home machine and FastMail.FM on the web, so that you see the same folders and messages wherever and however you access your email.
http://www.fastmail.fm/help/remote_email_access_pop_imap_and_smtp.html
Of course there are many FREE Email services.
The big ones are AOL, Google, Hotmaill and Yahoo.
These also offer IMAP service.
Do you prefer IMAP or POP?