PINE is an Acronym for Program for InterNet News & Email.

It's a console based mail client written at The University of Washington but licensed under non-Free terms, so that many LinuxDistributions (such as Debian) do not contain it. Features include

• Support for Roles - This allows you to easily assume different Roles (ie. From Addresses / Signatures) when composing mail.
• Excellent IMAP/IMAPS Support
• It's very quick and can be used over any SSH connection, unlike other graphical MailClients.
• Very simple menu and key configurations unlike other console mail clients such as Mutt which take a lot more learning. (Of course this can also be construed as a weakness.)
• It's not MozillaMail

A major disadvantage is that it will not check for new email in multiple INBOXes automatically: you need to press Tab.