Do any of you guys have recommendations for an email client that you think is private and secure?

Currently I pay for email hosting, so I know the company and servers where my emails are stored and I choose to trust them. The only issue is that, from a usability standpoint, the email client that I actually use to access my emails is terrible; both on the desktop and mobile app.

While I'm satisfied with the privacy and security of my current email client, I just can't be as productive as I need to be with it, so I'm looking for another, much better option. I expect I'll have to pay for this service though as I know that 'free' email clients are paid for with your personal information that has been obtained by scanning/data mining your emails.