4.3BSD/usr/lib/Mail.help

    Mail   Commands
t <message list>		type messages
n				goto and type next message
e <message list>		edit messages
f <message list>		give head lines of messages
d <message list>		delete messages
s <message list> file		append messages to file
u <message list>		undelete messages
R <message list>		reply to message senders
r <message list>		reply to message senders and all recipients
pre <message list>		make messages go back to /usr/spool/mail
m <user list>			mail to specific users
q				quit, saving unresolved messages in mbox
x				quit, do not remove system mailbox
h				print out active message headers
!				shell escape
cd [directory]			chdir to directory or home if none given

A <message list> consists of integers, ranges of same, or user names separated
by spaces.  If omitted, Mail uses the last message typed.

A <user list> consists of user names or aliases separated by spaces.
Aliases are defined in .mailrc in your home directory.