BSD Mail appears to be the default mail program used by SDF where 
I keep my web pages and my memory is pitiful so here's a cheat sheet

For example:
            Delete message 1 & 3 of a list of 3 messages
            d 13 <ENTER>
            BAM that's it! 

            Send a new mail
            Type mail joe@blow.com
            type Subject then the text of the message
            To send type <CONTROL>d
            that's it
		

t[message list]	 	type messages
n			go to 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 messages(to sender and recipients)
R   [message list]	reply to messages(to sender only)
pre [message list]	make messages go back to /usr/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
ch [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 distribution names 
                        separated by spaces. Distribution names are 
                        defined in .sendrc in your home directory.
& ~?			Display list of ~ (tilde) commands, for 
                        information about added features and operations