PINE (Program for InterNet News & Email) is a console based mail client written at The University of Washington.
PINE has over 25 Million users and has some very nice features.
The major disadvantage with PINE is that it will not check for new email in multiple INBOX?'s automatically. It will do this well if you press Tab however. Also some OSS Fanatics have issues with it's licensing as you cannot redistribute modified code or binaries, they must be distributed seperately. This keeps it out of some major distributions such as Debian.
You can get more information about PINE at it's homepage http://www.washington.edu/pine/
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