http://www.opera.com/products/desktop/m2/

Opera Mail is integrated with Opera's web browser - lets you send, receive, & search your e-mail quicker than with conventional e-mail programs....(Details)

http://pyric.org/qm/

Qm is an extremely small, fast program for sending E-mail. Its size and flexibility make it ideal for those times you want to quickly send messages or files without starting a large E-mail suite. Free download....(Details)