from(1)
NAME
from − show who mail is from
SYNTAX
from [ −f [ mailbox ] ] [ −s sender ]
DESCRIPTION
The from command prints out the mail header lines in a mailbox file to show you who your mail is from. The -f option causes from to examine the mail header lines in your mbox (or the specified file). If the -s option is given, then only headers for mail sent by sender are printed.
FILES
/usr/spool/mail/*