There's an problematic link on https://help.directadmin.com/item.php?id=51
See the readme file is pointing to https://www.nobaloney.net/downloads/spamblocker/DirectAdminSpamBlocker4.2.2/ which returns 404 Not found.
Code:
Note that there are entries in the /etc/exim.conf that should
be manually set for your system. See the readme file for more
information. (See the section labelled MANDATORY CHANGES to
the SpamBlocker.exim.conf file).
See the readme file is pointing to https://www.nobaloney.net/downloads/spamblocker/DirectAdminSpamBlocker4.2.2/ which returns 404 Not found.