Does not sound like spam. To verify an email adress they usually send some HTML-Code, which loads a Gif-File from their server. If the file is loaded, they know that the email addy is good - even if you do not reply. Was there some kind of picture in the email? Or a reference in the email-code, if it was html?

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.