Hello ,
You can check if there are any old formmails on your server with version 1.6
The following command will give you a list of all those files in list.txt
find /home/*/public_html/cgi-bin -name '*orm*ail.pl' | xargs grep -l "Version 1.6" > list.txt
to list all active formmails on the server
find /home/*/public_html/cgi-bin -name '*orm*ail.pl' > list.txt
Just pass this text file to the shell script which take the ownership of these files to root and also makes the permissions 000. This way your users cannot install the formmail.pl again as it already exists.
Please let me know if you need the shell script, i'll provide it to you if you desire.
Also I presume you are using Formmail.pl from
http://www.scriptarchive.com/formmail.html
The version 1.92 is almost spam free you can let your users have it but remove all previous versions.
Rest as per you decide.
Let me know if this works for you.
Regards,