I suppose this is one of the main issues of cold e-mailing already. But in the specific case of wanting to reach out to local businesses that don't have websites, what is done to get their e-mails? I know you cannot sms to them in a cold e-mailing fashion because your telephone company blocks your number due to spam (learned it the unpleasent way). And I suppose you cannot use SMSing API's because their terms of service requires the reciever to have submitted a consent form for it. So SMSing is ruled out.
So what is the way? How can businesses with no websites be found?
So what is the way? How can businesses with no websites be found?