I wanted to share my experience in case it is helpful for anyone else. I hope this is the right place to do it.
I have been using a service called Mail Baby (https://www.mail.baby/) to send email. Originally it was offered as part of my shared hosting plan, but when I had to upgrade to a VPS I ended up subscribing to Mail Baby separately. It has been working very well. They can handle bulk email sending (no speed limits that I am aware of), and they work hard to keep spam out of the system and thus their reputation for positive mail delivery is high. It’s a no-frills kind of service, just SMTP and no fancy formatting like in MailChimp, but it is much less expensive. $1/mo plus $0.20 per thousand mails.
if you’re looking to send bulk email through Church Admin then this might be a great way to do it. I have it configured at the server level, but you can also just put in the SMTP information into the plugin and it should work straight away.