If you're ready to pay 5$ each month for each thousand subscribers, Buttondown seems like a great tool. It does offert paid subscriptions as well if you want to earn money with your content.
I have no affiliation with them but I did speak to the guy who runs Buttondown on my podcast. He went over how it's built and deployed at: https://runninginproduction.com/podcast/70-buttondown-lets-y...
He has clients with over 100k+ people on their list and has put in a lot of thought and leg work to ensure good deliverability rates. It's also been running for ~5 years.