This module turns dominique@dominiquedecooman.com [4] into

<a href="mailto:&#100&#111&#109&#105&#110&#105&#113&#117&#101&#64&#100&#111&#109&#105&#110&#105&#113&#117&#101&#100&#101&#99&#111&#111&#109&#97&#110&#46&#99&#111&#109">

The code in the module can be found on http://drupal.org/node/151638 [5]
I just put it in a little module ready to be downloaded and installed.

Installation : Just put the module in your sites/all/modules folder, install the module and turn the filter on for the right Input format in admin/settings/filters

EDIT: Or you can just use the spamspan module http://drupal.org/project/spamspan [6]