We simply banned them.

If I recall correctly, they were explicitly mentioned in our t&cs, and we had a filter on our ftp server which would quarantine them & email an explanation to the uploader.

For FormMail, we automatically substituted the London.pm nms drop-in compatible version (mentioned in the article). For the others, we provided a link to the nms versions and had our support team reach out and offer assistance with converting their site to use them.

It saved us endless trouble - the MSA FormMail was responsible for so much spam in the 2000 - 2002 period.