-e     Test for the presence of mail in the system mailbox. The mailx utility  shall  write  nothing  and
       exit with a successful return code if there is mail to read.

-f     Read  messages  from  the  file named by the file operand instead of the system mailbox. (See also
       folder.) If no file operand is specified, read messages from mbox instead of the system mailbox.

-F     Record the message in a file named after the first recipient. The name is the  login-name  portion
       of  the  address found first on the To: line in the mail header. Overrides the record variable, if
       set (see Internal Variables in mailx .)

-H     Write a header summary only.

-i     Ignore interrupts. (See also ignore.)

-n     Do not initialize from the system default start-up file. See the EXTENDED DESCRIPTION section.

-N     Do not write an initial header summary.

-s  subject
       Set the Subject header field to subject. All characters in the subject string shall appear in  the
       delivered  message. The results are unspecified if subject is longer than {LINE_MAX} - 10 bytes or
       contains a <newline>.

-u  user
       Read the system mailbox of the login name user. This shall only be successful if the invoking user
       has the appropriate privileges to read the system mailbox of that user.