Below the Line Marketing (BTL) is a targeted marketing strategy that involves reaching already-engaged customers to convert sales or drive already-aware customers to engaging with your brand.
This is most commonly executed through email marketing, since you can enhance the targeting by segmenting your database and there’s a strong likelihood that subscribers to your emails are existing customers.
The biggest benefit to BTL is the high conversion rate, with the biggest drawback being the fact you don’t reach as many consumers.