Groupon sold my e-Mail address

The idea behind groupon is to make it easy (and cheaper) for new customers to try out a service or product. The whole site really looks like racket but I used it some time ago. I have the common practice that I create an e-mail address for every single service I register to. So I used an e-mail address of the style "mymail-groupon@mydomain.tld" for it. Today I got an e-mail with the subject "Abmahnung Ihrer aussehender Rechnung über 262,00 Euro" (impolite german for "Reminder for a payment about 262 euros") from an debt collecting agency. The full From-line looks like this:

From: "K&LWallArt Inkassoburo" <barbara.schrank@t-online.de>

In the mail, they very bluntly tell me to pay the money within 3 days or else. They gave a footer looking like this:

K&LWallArt Ltd.
Telefon: (+49) 237 4XXXXXX
Umsatzsteuer-Nr.: DE242039481 Asperg
Direktor: Nelli Krüger

Out of curiosity, I called the number – that I removed from the footer for privacy reasons of the real owner – and a german guy was on the other side of the line – which I expected since it is a number from Iserlohn-Letmathe. I only asked if I am connected to the "K&L WallArt Ltd." and he said no so I excused me and said goodbye. I hope for that poor guy that they use different numbers for different targets. @Groupon: You suck! Don't sell my e-mail address! Or: don't let one of your partners sell my e-mail address! Or: Pay attention to the e-mail addresses stored in your system! Ah I nearly forgot: of course there was an attachment named "Produktnummer- 1580698766 XXXX XXXXXXXXXX.zip" (the Xs where my name, it seems that another guy called Markus Kowalski also uploaded it to virus total) contaning another zip file named "Mahnung Ihrer Rechnung vom 04.04.2013.zip" containg a file named "Mahnung Ihrer Rechnung vom 04.04.2013.com". /p Update (2013-08-31): A similar thing happened to my Hamachi / LogMeIn e-Mail Address. Update (2014-12-06): And Adobe too.