"there is no cost to to sending an email" Only if you're not paying for the servers or the copy-writers, etc. "so it's more difficult to determine what copy a

"there is no cost to to sending an email" Only if you're not paying for the servers or the copy-writers, etc. "so it's more difficult to determine what copy actually works." That doesn't follow. Any sort of tracking, A/B testing, etc. that you could do with junk mail, you can do with spam or more accepted email marketing - and probably more cheaply.