I mentioned this on another post... I use and recommend ConvertKit for a simple yet powerful email marketing tool.
I did a little blog post (well not that little) that compares ConvertKit vs MailChimp.
Yes there are affiliate links in that post and yes I chose ConvertKit. But give it a read for some insights on ConvertKit and some screenshots of the insides to check it out.
The biggest factor for me choosing ConvertKit, and I explain this in the article, is that ConvertKit considers an email to be an account. So you won't have the same email on multiple lists. Instead you'll have a subscriber, and be able to see the forms they've subscribed through and the sequences they are in, and much more.
You can read it here > ConvertKit vs Mailchimp: A comparison