On average, only 18 per cent of unsolicited emails are ever opened and of those, only 3.3% are read by the recipient. According to a survey among direct marketing providers, only 2.6% of these are immediately unsubscribed to. Meaning future email from the sender will not get through to the person they’re addressed to. That leaves only 0.7% emails that actually get through, are opened and are read.
Not acted upon, mind you – just read.
… assuming the person they’re meant for is the person on the end of the email address. Lists from list brokers are notorious for falling out of date very quickly. Or already being out of date by the time you come to use them.