I've got about 700,000 single-opt-in email addresses. I'm not a big fan of spam. Would I be crazy to just delete the file without using it?
Delete it. Would you delete the mail you are thinking of sending? unless you build a db of addresses then forget it...
Depends on what you have to lose. - Reputation - Spam complaints to your host or ISP - Cost of sending If all of the above are not an issue go ahead and try to "warm the list up" with a free offer of some type if they double opt-in. Once they double opt-in (on average only 10% will do so) you can then attempt to make a sale. Good luck!
Did you buy/find the list or did you collect the emails yourself? If the latter, I agree, definitely try to get them to double opt-in. I'd actually expect a number much less than 10% of the 700,000, but really any percentage would give you a solid and much more responsive list.
The emails are ones I collected over the years via my various websites. And technically my privacy policy on those sites doesn't exclude the possibility of contacting them in the future.
Over the years means they have forgotten about you. If you mail that list you'll get a lot of spam complaints.