/bin/mail doesn't handle piped in data
/bin/mail is now included in the Haiku image (thanks!) but doesn't work when piping the message text via standard input (the BeOS one does work that way too).
Needs an end-of-file detection as well as the manual period on a line test. If you want to get fancy, only use the "." end of message marker when reading from a terminal. gets() returns NULL at end of file, should test for that and break out of the line reading loop at that time. Example user level usage to test it (make sure the last line of the listing gets through too):
ls | mail -s Testing me@…
Applications/Mail → Applications/Command Line Tools
new → closed