More or less all iOS and Android mail clients. https://www.imore.com/best-email-apps-your-iphone-and-ipad https://www.imore.com/best-email-apps-your-iphone-and

More or less all iOS and Android mail clients. https://www.imore.com/best-email-apps-your-iphone-and-ipad https://www.imore.com/best-email-apps-your-iphone-and-ipad They do support imap, but they process your messages on their proprietary cloud service. What sane person would agree to that? In the US there seems to be not a lot of concern about data protection yet, so there seems to be a market for those services.