>Dear NetBSD,
>
>I managed to lock all users other than root out of my V1.6 system.
>In the name of Internet security, I used chmod to keep etc, home, and other
>directories and files from being seen from the web. I soon realized that I
>could no longer log in as a regular user:

 :)

...once you get this solved (if you can, I dunno, seems like a fubar?), 
you can do what you originally wanted to do by simply editing the passwd 
file so the home account of the users is /bin/nologin and make a file 
named /bin/nologin that contains a message, something like:

#!/bin/csh
Sorry, this account is only allowed to send/recieve email from this 
server. System logins are not permitted for your account. Please contact 
the Sys Admin for details.

HTH