Buy (sorry, "rent") a domain name (about $10 a year or less), and setup a catch all on it. Then use a different email for every online service. Alternatively, some free web mail providers (e.g. Yahoo, at least for me, maybe not for you) let you have multiple email addresses as well. For Yahoo, you could have a stem such as "mymail-" and then all the different emails you create would then be of the form "mymail-mtgox@yahoo.com". YMMV.