[hypermail] -u and -x switches

(In case you couldn't guess) I'm working with Hypermail again. A while back I asked about how -x and -u work:

  http://dev.hypermail.org/mail-archive/2001/Dec/0013.html

And again, today, I can't seem to understand. I created three files each with one email message and tried combinations of:

   cat 1 | hypermail -i -x
   cat 2 | hypermail -i -u
   cat 3 | hypermail -i

Can someone explain what -x and -u actually do?

The man page also says:

           When using the -u option, don't send any messages that
          Hypermail  has already processed. If you want Hypermail
          to recognize that some messages are old  messages  that
          shouldn't  be  added  to  the  archive again, send it a
          mailbox with a complete set of messages and  avoid  the
          -u option.

I think that says "Don't feed the same message to hypermail twice." Is that still true, even with usegdbm = On?

BTW on http://hypermail.org/source/docs/hypermail.html

   example 2: cat "/var/spool/mail/wu-ftpd" | hypermail -i

   2. This reads the file /var/spool/mail/wu-ftpd from standard input

      and will save the output in a directory called wu-ftpd in the same
                                                     ^^^^^^^

should be "archive".

-- 
Bill Moseley
moseley_at_hank.org