Another alternative, if you're technical enough or may have a friend to help, is to setup your own email server and that would technically make you the email provider.
End-to-end encrypted app for email, calendar, and contacts, requiring no personal data, with open source code and quantum-resistant security.
Disroot is a platform providing online services based on principles of freedom, privacy, federation and decentralization.
I would recommend that you use the email provider's official web client and mobile app. However, if you're wanting options to use 3rd-party clients or simply want more than what the provider has to offer, then here's a list of options below.
Do note, if you plan to use Tuta, you may not use 3rd-party clients with their service. Tuta does not support the protocols IMAP/POP3/SMTP as they mention "...we cannot guarantee end-to-end encryption of your data."
Read more about Tuta and 3rd-party email clients on their support page.
Cross-platform email client providing POP/IMAP support, robust filtering, multiple accounts, and chat. Extendable via add-ons with RSS/Atom, etc.
Open-source client enhancing Thunderbird with more features and bug fixes. Offers security patches and multi-row descriptions like Outlook.
K-9 is an open source email client for Android with multi-folder sync, email signatures, Bcc-to-self, return-address configuration, keyboard shortcuts, Exchange Support, message flagging, IMAP deletes, saving attachments, configurable notifications and more.
KMail is the email component of Kontact, the integrated personal information manager of KDE. Kontact is a personal information manager and groupware software suite for KDE. It supports calendars, contacts, notes, to-do lists, news, and email.
Mail is designed to let you manage your email quickly and effortlessly. Its interface is based on conversations, so you can read an entire discussion without having to click from message to message.
