No I didn't try it.
I have to try it in a very busy email hosting server. Thanks to MSFE, thousands of spam mail is blocked. So if I was right, even if I test it for few minutes my customers' inboxes will be flooded with 100's of spam mail.
But if no one knows the answer, I guess I will have to test it.
EDIT: It works!
*@*.sampleshop.com works for all subdomains of sampleshop.com, and not for other domains.