Mutt

I use a cool (lean, mean and downright sexy) mail user agent called Mutt. Mutt can be configured to do anything (except perhaps bark excitedly and run around in circles wagging its tail). Take a look at my .muttrc to get off to a quick start. You can get lots more .muttrcs and other Mutt config files at http://www.mutt.org/links.html#config

In my muttrc, I've just changed my name to "Foo Bar" and addresses to stuff like foo@example.com to foil all those nasty spambots out there, busily scraping e-mail addresses like these (clumps of random ASCII formatted to look like e-mail addresses, generated by a great little tool by Ron F Guilmette. Here's a Wired article on this tool, which shall not be named here because bots, deathly afraid of it, will avoid any page where they think a copy is installed.

I also happen to be one of the maintainers of a (currently fast asleep) project to build a Mutt newbie guide, currently hosted on Sourceforge. Others on this project include Mrinal Kalakrishnan, Kai Blin, Telsa Gwynne, Sven Guckes, Charles Curley and several other folks from the mutt-users list.

Pine

Pine is an old client - developed at the University of Washington. It's become part of the standard install on nearly every version of unix, and comes in a windows port as well.

It works pretty much out of the box, but you just have to set the user domain to whatever you want it to be (or it sends out mails as localuser_name@localhost.localdomain). So, if your name is joe@example.com and you use pine, create a user called joe and set the user domain (from the main menu, it is S-Settings and C-Configure) to example.com. Finally, set your smtp server to 127.0.0.1 in the same place. There are lots of other options there - play around with them. See The PINE configuration notes.