Does CoolerEmail “filter” for duplicate addresses and invalid addresses?
Yes. CoolerEmail purges all duplicate email addresses from your list (so the same email address won’t get more than one message) and advises you of invalid addresses (so you can delete the address or try to fix it). CoolerEmail also automatically adds people to your list who have subscribed and removes those who have unsubscribed—the whole list management process is automated for you!