使用PHP mail（）发送电子邮件时使用什么作为“垃圾邮件过滤器”？

Question

I have a classifieds website, and on each classifieds page, there is a form for tipping a friend where you just enter the persons email-adress and the tip will then be sent. The form is submitted to tip.php where all "magic" happens with checking and sanitizing etc etc...

Lastly I use php:s mail() function to send the email from tip.php...

Now, I wouldn't want spam-bots and automated robots etc to send mail and blacklist my server. What should I do?

One method which I would rather NOT use is logging IP:adresses of senders in a table (MySql) and then allow only x emails per sender.

As I said, the above solution is nothing I would prefer, there must be an easier way.

Is there any method you know of?

Is there any application to install maybe, on a linux server which does the job?

Thanks

Answer 1

I would say that the most used method would be captcha. This will ensure that the one that sends the email is a man, but everything can be cracked. So I would recommend to find a really good one, just type captcha into google and you are good to go. Also you can use another method/thing to make it more viable, e.g. some question that can be answered a simple mathematical problem, etc.