smbaccess is used to restrict access to a Samba server from clients with certain hardware network addresses. However, this mechanism only works if the client and the server are operating in the same subnet with a direct network interconnection or in a switched network environment since the hardware network address is determined from the IP-number using the arp-cache visible in /proc/net/arp under Linux. smbaccess is invoked during the login process. If access according to the access rule is not granted, a non-zero errorlevel is returned as error code and the login process is stopped.
Rbl-milter extends the capability of sendmail to add an X-RBL-Warning to email messages that originate from open relays without having to write new m4 macros yourself. With this milter, an admin can have messages tagged that come from open relays and allow their users to do filtering on their own. Rbl-milter also has the capability to check connections against multiple RBL lists.
Zoneadm is a CGI application to allow a DNS hosting site to delegate simple zone change privileges to remote users via a web interface. It allows a remote user the ability to make A, CNAME, PTR, and MX record changes to a zone that the DNS site administrator has given them permission to modify. It does some sanity checking on the information entered by the user, but it may not be foolproof and assumes some knowledge of DNS resource records by the users.