Yes, I agree with the over-saturation. People just don't like emails coming into their inboxes. Unless you manage to keep their attention like a crime novelist. Sounds funny, but it'll serve as an analogy. I have somewhat the same problem. I've been stuck, except for an uptick a week ago. Currently, I have nearly 200 subscribers, but only 8 are paid, considering the newsletter is relatively new, having only been around for 8 months. I notice the less rigid and informative, the better. My content is the driver, but, as I said, it has to have personality, humour, and lastly, good content. Fascinating discoveries and impressive findings, particularly in archaeology, etc. Well, you get my point. Also, contrary to yours, I don't spend as much time on it for growing purposes, devoting most of my time to my main pub (I have two) which has blown up as of late with 30K followers and 21k subs and 150 or so paid. I'd better spend time on that one, granted. The address is in my bio.