From the English README and pksd_help.en files:

If you have configured the mail server component of the key
server, there is one more step you need to take so that the server
can actually handle mail.  In your aliases file (usually one of
/etc/aliases or /etc/mail/aliases), create the following lines:

    pgp-public-keys: "|PREFIX/bin/pks-mail.sh PREFIX/etc/pksd.conf"
    pgp: pgp-public-keys

Or, if you are using qmail, create these files for use with the 
dot-qmail(5) framework :

cd /var/qmail/alias/
echo "&pgp-public-keys@localhost" > .qmail-pgp
echo "|preline /usr/local/bin/pks-mail.sh /usr/local/etc/pksd.conf" > .qmail-pgp-public-keys 

You might also need to add aliases for the mail addresses you
configured in pksd.conf.  

You will also need to make sure the permissions on PREFIX/var/incoming
allow both the mailer and whatever user the pksd program runs as
to insert and delete files.

OpenPGP public email key servers allow users to exchange public
keys running using the Internet and properly configured e-mail
servers.  This service exists only to help transfer keys between
PGP users.  It does NOT attempt to guarantee that a key is a valid
key; use the signatures on a key for that kind of security.

Each keyserver processes requests in the form of mail messages.
The commands for the server are entered on the Subject: line.
---------------------------------------------- ======== -----
Note that they should NOT be included in the body of the message.
--------------------- === ---------------------------------------

        To: pgp-public-keys@keys.pgp.net
        From: johndoe@some.site.edu
        Subject: help

Sending your key to ONE server is enough.  After it processes your
key, it will forward your add request to other servers automagically.

For example, to add your key to the keyserver, or to update your key
if it is already there, send a message similar to the following to any
server:

        To: pgp-public-keys@keys.pgp.net
        From: johndoe@some.site.edu
        Subject: add

        -----BEGIN PGP PUBLIC KEY BLOCK-----
        Version: 2.6

        <blah blah blah>
        -----END PGP PUBLIC KEY BLOCK-----

COMPROMISED KEYS:  Create a Key Revocation Certificate (read the PGP
docs on how to do that) and mail your key to the server once again,
with the ADD command.