SWGUY makes the most important point...
Your action will "oblige" people to receive your newsletter - even if they don't want to.
So... what a LOT of people will do is simply mark the incoming email as spam or junk.
As Scott says... get enough of these, and your outgoing email address will be flagged as that of a potential spammer. Blocking engines will then blacklist you, and you will find that your host server could also be blacklisted - affecting everyone who shares that IP.
So... far from being competitive, you risk causing huge problems, not only for yourself, but others too.
Far more efective would be to incentivize sign-up to the newsletter. Offer subscribers a discount coupon on their first purchase (easy to configure in ZC).
To "force" a behaviour onto potential customers is not the best way to go.