What are your measures for securing scripts that send out e-mails so others cannot use it maliciously? I'm look for any and all ideas that you've had or used in the past that helped.
What I plan on doing is:
REFERER check (I know this isn't "perfect" but used with other sections, but any help is better than nothing)
IP time checker (Each time the script is launched it logs your IP and compares it to a database of times and IPs. If the IP executed the script within the past X minutes, the script will fail to execute.)
Message substitutions (Filter out anything after a space or comma in all the to/from/bcc fields to disallow multiple addresses)
I know on a scale from 1-10 for security, this probably only hits a 4 or 5. What other methods can you think of?
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