I actually use the service you described. It is called http://anonaddy.com .

I'm not affiliated to them (discovered them on Producthunt I think) but I use it all of the time for one-off eCommerce websites, newsletters, etc. you can have your own custom domain and anything before the @ is a wildcard and gets automatically created.

It is super easy to "delete" or stop the forwarding of email to these addresses