“At one time, marketers simply emailed all of their contacts every single campaign they created. This approach is called ‘batch and blast’ (marketers would collect, or ‘batch’, all of their email contacts and ‘blast’ them with a campaign). Batch and blast tactics can lead to high unsubscribe rates and lower overall email deliverability.”
Stay away from “batch and blast” practices, which involves creating one email campaign and sending it to every consumer on your list. Customized campaigns are what people want, especially millennials who are now very used to brands catering to them with personalized services and product offers.