twitmail is a curses-based mail-like interface to twitter. It also can be
used as a command line app for sending and receiving tweets. In both modes
it remembers the last thing you read and only shows you newer posts (ie, it
reports nothing when you have no updates to read). It'll collect all the
new posts as well (up to a configurable limit), to ensure you haven't
missed anything important.

WWW: http://www.hardakers.net/code/twitmail/