This is in no way encryption. However UA support for "mailto:" is at best patchy the recommendation is to avoid it completely, or failing that restrict yourself to specifying a single address.In no time at all, I fear the questioner would be back asking how to protect his form from spam. Search for mailto:xxxnullxxxxxx.xxx and replace with . That way, when the old mailto: link is clicked, users will be directed to theAll those members who innocently place their email addresses in a mailto: link are at risk of have them scrapped and added to some Americans spam list. - Other ALL-UPPERCASE words like e.g. NO SPAM NOSPAM WHATEVER I DONT WANT SPAM etc. will simply be dropped (replaced by an empty string).