Pine

pine is an easy to use text menu based mail client. If you are receiving mail locally on your machine you can just type pine to send and receive mail. If you are not then it might be a lot more difficult. pine does not work well with POP servers, but can connect to IMAP servers. In pine you have a list of commands at the bottom of the screen. Here is a quick list of commands from the main menu:

?                    Help
c                    Compose a message
i                    Message Index
l                    Folders
a                    Address Book
s                    Setup
q                    Quit

When you are composing an email message the commands are almost the same as the pico editor commands. When you are finished with the message you can press Ctrl-x to send it.