I think there are many possibilities for this good idea
I suppose it could be done with or without the mailto - but spiders that search for the mailto: will render that one pointless. Unless, however, no mailto is used - OR - for every symbol used in the address, it is replaced with its ASCII value, which in HTML is in it's raw ASCII format, but when clicked/mouse overed it renders without any javascript..
HTML Code:
<a href="mailto:jimpsed@hellp.com">jimpsed@hellp.com</a>
once converted to ascii;
Code:
<a href="mailto:jimpsed@hellp.com">jimpsed@hellp.com</a>
[EDIT] - it seems the ascii characters are being pre-processed before being entered into the database/being displayed. It works if you code this and then display it from a HTML web page though - try the attatched file. The source, you see the raw ascii characters. When viewed in a browser, all the characters are rendered.
This "solution", however, is only good if the spiders are only going through the HTML of a web page - I do not know, though.