"Mail a friend" without Spam

[gygabite]

I stand and must make a "mail a friend" feature. The only requirement I have received is that it should be as close to spam-free as possible.

My framework is that I have jsp available (of course, with underlying web and app server - but it is not necessary to carry out the task?).

I've looked a bit online and found CFFormProtect (http://cfformprotect.riaforge.org), which unfortunately makes use of Cold Fusion. I would rather stick to jsp, where possible. Someone who is familiar with a similar extension? Whether it is open source or cost money is no problem (in other words, in real borders ).

I've also looked a bit on captcha. It seems I will give a bad user experience, so I would prefer to avoid. Charging the user to enter his own mail and then confirm it is also a possibility, but also one I would rather avoid.

All ideas and the like is more than welcome.

[kelfro]

Captcha has been proven standard solution!

There is captcha solutions for JSP.

It will link to you is so unusual that I do not think that you can find a ready
solution. But most of the items are relatively easy to code.

[gygabite]

If I have to be honest I am not come forward with what the solution should be. I think I leave it to the store to decide what they would ideally like to see.

If you would want points simply toss a response