Here is a solution for mail obfuscation (obfuscation occures while the page is saved, not while is it showed)

the page.php (mysite/code/page.php) or any instance of it:

class Page extends SiteTree {
	
	...
	
	public function onBeforeWrite() {
		// obfuscate mailto-links
			// replace mailto-mailadresses within href attributes of links
			if (preg_match_all('/href="(mailto:.*?)"/', $this->Content, $matches)) {
				$searches = array();
				$replaces = array();
				for($i=0; $i<count($matches[0]); $i++) {
					$link = $matches[1][$i];
					$obfuscatedLink = "javascript:defuscateMailTo([";
					$first = true;
					for ($j=0; $j<strlen($link); $j++) {
						$obfuscatedLink .= ($first ? '' : ', ') . (ord($link[$j]) + 111);
						$first = false;
					}
					$obfuscatedLink .= ']);';
					array_push($searches, $link);
					array_push($replaces, $obfuscatedLink);
				}
				$this->Content = str_replace($searches, $replaces, $this->Content);
			}
			// replace mailadresses within the links themselfes
			if (preg_match_all('/<a [^>]+>([^@]+@[^<]+)<\/a>/', $this->Content, $matches)) {
				$searches = array();
				$replaces = array();
				for($i=0; $i<count($matches[0]); $i++) {
					$link = $matches[1][$i];
					// this would convert mailadresses into text
						/*$obfuscatedLink = "Mail";*/
					// this would replace the "@" with " at " and remove the domain (for example ".com")
						/*$obfuscatedLink = substr($link, 0, strpos($link, "."));
						$obfuscatedLink = str_replace("@", " at ", $obfuscatedLink);*/
					// this would replace the "@" with " at " and the "." with " . "
						$obfuscatedLink = str_replace("@", " at ", $link);
						$obfuscatedLink = str_replace(".", " . ", $obfuscatedLink);
					array_push($searches, $link);
					array_push($replaces, $obfuscatedLink);
				}
				$this->Content = str_replace($searches, $replaces, $this->Content);
			}
		parent::onBeforeWrite();
	}
	
}

class Page_Controller extends ContentController {
	
	public function init() {
		parent::init();
		Requirements::javascript("mysite/javascript/rosa.js");
	}

}

the javascript:

// defuscates obfuscated mailto adresses
function defuscateMailTo (mailArr) {
	var mail = "";
	for (var i=0; i<mailArr.length; i++) mail += String.fromCharCode(mailArr - 111);
	window.location.href = mail;
}

This works great! Thank you very much!

Is there any update to the second conditional statement?

 // replace mailadresses within the links themselfes

Lovely. The posted javascript should be

  for (var i=0; i<mailArr.length; i++){
       mail += String.fromCharCode(mailArr [ i  ] - 111);

   }

I've been using this script on all my sites for a few years now, but I've been getting reports from clients using SilverStripe 3.0, that sometimes when they make a change to a page including an e-mail address, chunks of text are being wiped out upon save. Any idea why this could be? Does it need updating for SilverStripe 3.0?

Hi there, to get this working. You paste the code into the mysite/page.php. Which is linked to the Javascript file.
Is there anything else to do? (with the templates side of things.)
I have had trouble getting things to work.
Cheers Stuart

I've since started using this module: https://github.com/axllent/silverstripe-email-obfuscator which I've found to work much more reliably.

James