Many networking programs can print this message, including from(1B), lpr(1B), lprm(1B), mailx(1), rdist(1), sendmail(1M), talk(1), and rsh(1). The command prints this message when it cannot locate a password file entry for the current user. This error might occur if a user logged in just before the superuser deleted that user's password entry, or if the network naming service fails for a user who has no entry in the local password file.