Why you should never, ever delete your spam email
pcworld.com
However, the well-intentioned function also harbors a danger, at least in the case of fraudulent messages. This is because you inadvertently inform the sender that your own e-mail address actually exists and is actively managed. Spam crooks send millions of emails every day, sometimes indiscriminately to randomly generated recipient addresses. They are often unaware of whether the accounts they write to really exist or whether messages are read there–until users click on the unsubscribe button. The scammers then receive a request to stop writing to the email address in question, whereupon, of course, they do exactly the opposite.