Introduction to inetd and xinetd
inetd
imapd: 10.0.0.0/255.0.0.0, 1.2.3.0/255.255.255.0
This would allow access from 10.* and 1.2.3.*. Now, for
everyone else, you would add something like this to hosts.deny:
imapd: ALL: banners /etc/banners
In /etc/banners, you need to have a banner file for each
service using a banner. For imapd this would be /etc/banners/imapd, and the file might contain:
* OK %h IMAP4rev1 v12.264 server ready
xinetd
Resources
http://www.macsecurity.org/resources/xinetd/tutorial.shtml