We have about 700k users who have opted in to our newsletter but we only send one a couple times a year. As a result mailchimp's costs are way too much so we've used Sendy the past couple years. Our emails are definitely not spam as they're announcing new products/features/company related/etc and again, only a couple of times a year... but over time more and more often the newsletters end up in peoples spam folders. We're sending through SES so this really shouldn't be an issue but it does. I'm not sure if Mailtrain will do something that sendy doesn't do to make mail deliver better but it really seems more like mailchimp gives some kickback or deal to gmail/etc or gmail just knows that people using mailchimp are paying a lot so that goes through...

Anyway long story short, Mailtrain sounds interesting if it can solve this issue... but it's really not just spam that gets blocked as spam these days, its a major pay to play game and its the email companies that are getting paid, not the people getting the emails.