I built this little API as I wanted to do this in one of my projects, looked around and found that it was either quite difficult to do, had a bunch of extra stuff that was useless, didn't support SMTP/IMAP, etc...
I tried to price it at 5x less than Nylas, because I have less features and it's a new API. It's free in the development mode, if you join the waitlist I can invite you, I'm only limiting it because the payment system isn't fully built, and webhooks don't work in development, but I'm going to add those soon.
thanks for reading this small rant, Dan
PS: I will give this away for free, if you give me feedback.