ASP.NET prevent bot/spam attack from a comment form
<p>I have a simple contact us / comment from in my website and this form will send email containing the comments, etc after it is submitted. I have used NoBot control from ajaxcontrol toolkit for several times but it seems that this control did not prevent the spam/bot attack 100%. </p>

<p>The client insist that this form should not have any capcha code or something that users have to insert in the form. So what is the best way to handle the spam/bot attack for my current case. </p>

<p>Thanks.</p>
