I've seen a ton of information on the web about choosing and using email apps and systems. I've even debated making a course about it from time to time. But I never felt like I was the right person to put it together. Thankfully, The Sweet Setup just launched (note: this is an affiliate link) just a course and I can tell you that it's well worth your time and dollars.
I'm only part of the way through the videos at this point (I was given early access), but I'm already seeing how my email practices could use some improvement. Shawn Blanc and team have done an excellent job in putting this together. I highly recommend you give it a look. And do so soon! They have launch pricing on right at 20% off!