Probably "Matt's Formmail" though there are other scripts out there with the same name and purpose.
Most webmasters will tell you that their http logs are filled with records indicating attempts to execute /cgi-bin/FormMail.pl and Formail.cgi and all permutations of case. These are so-called "script-kiddies" trying to exploit weaknesses in this well known Perl script. I don't think too many sites run insecure versions of that any more, so these attempts probably deliver very little fruit, but the point is that these are people up to no good. An IDS system might immediately add their ip's to a blocked list just on general principle. There are many other less common, but still indicative, accesses. If I were using Formmail (I don't), I'd rename it. While security through obsccurity isn't much, it might just save you some trouble.
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