How do you get those subscribers in the first place? Ask them. Pitch them something. Offer something of value. Give them a free trial if they sign up to the new

How do you get those subscribers in the first place? Ask them. Pitch them something. Offer something of value. Give them a free trial if they sign up to the newsletter. Doesn't matter what it is, just find something useful to offer as a reward for signing up and make the offer incredibly visible. It doesn't need to be any more complicated than that.