<a href="mailto:spamtrap@jerrykindall.com" onMouseOver='myrealaddr=unescape("%73%65%6e%64%74%6f%6d%65")' onClick='url=this.href.split("@"); url[0]=myrealaddr; url[0]="mailto:"+url[0]; this.href=url.join("@")'>send me mail</a>
Here's how it actually looks when rendered in a document.