I have changed 3 autoresponders in the last 6 months. It's either they were becoming too expensive, lacked some features I'd want, or had poor deliverability.
Mailvio solved all for me: affordable price, awesome features that makes my work easy, and good deliverabilty. My lowest open rate in Mailvio has been 33.8%, while the highest has been 72.1%
I've never had it that good from any of the platforms I've tried