Ah, the mailto tag. The easiest way to let people contact you or your company from your website. Easily readable and clickable… and harvestable. Therein lies the problem. Spammers use email harvesting software to scan pages for email addresses to send their spam messages to. And, of course, the venerable mailto tag is the easiest thing for them to pull the address from.
So, some people started just having their email address on the page as the text version of the email address. You have to copy and paste it into your email program, but it still works. Unfortunately, the harvesting programs where updated to catch that, too.
Then people started encoding their address. Instead of email@example.com, it was emai… in the code. Still readable and copyable, but not clickable. And yet again, it appears that the spam filters have caught up and are able to harvest these encoded addresses.
Now many sites now use JavaScript functions to create the mailto links. The calling script simply passes the address and the domain as seperate arguments and the function combines them. Of course, if these specific functions become widespread, the harvesters will be updated to look for them as well.

Obfuscating email addresses is one of those continuous challenges on a par with the painting of the Forth Railway bridge.
Email scanners (or email harvesters) used by SPAMMERs to scan web pages looking for email addresses.

Obfuscation is a method of cloaking the email addresses to combat this, but as always happen, the SPAMMERs adapt.

The method discussed on the site below attempts to combat this using a different approach, and it appears to work quite well.

Have a look at the link below and give it a go.

http://johnhaller.com/jh/useful_stuff/obfuscate_mailto/