This page documents the HOOK_DIR configuration setting in FormMail.
Type Of Setting
HOOK_DIR is an OPTIONAL setting, which means...
OPTIONAL : you can change this setting if you need to, but the default value is fine for most circumstances.
Sets the directory/folder for your hook system scripts.
Set HOOK_DIR to a directory/folder path on your server where you store include files for the FormMail Hook System.
Note that this setting has to be a directory (folder) path, not a URL.
If set to an empty string (the default), the Hook System is disabled.
NOTE: on Windows servers, use '/' instead of '\' or double the '\', like this:
$HOOK_DIR = "";
$HOOK_DIR = "/home/mysite/public_html/fmhooks";