Postbox

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K-9 Mail is an open source email client focused on making it easy to chew through large volumes of email. K-9 Mail is designed for both novice and power users and offers lots of features for everyone. It provides features like Push IMAP Support, GPG & PGP/MIME support, Per Account Notifications, Unified Inbox, White and Dark Theme, and Signatures.

Zoho Mail provides ad-free email hosting for business and organizations. It's comes with intuitive migration tools, along with 24/7 dedicated migration support to ensure smooth, lossless migration from your existing email provider. With Zoho Mail, your organization can manage all their email, calendar and contact needs. Since Zoho Mail is part of the Zoho's suite of online productivity, it's easy to extend the capability in to more parts of Zoho's offering and essentially run your entire business with Zoho. Zoho is provided as a Freemium software, where the free plan supports up to 5 users in an organization.

Apple Mail is email client built specifically for the Apple eco-system. You can use Apple Mail on your mobile iOS device or your macOS desktop or laptop. It provides all the features needed to communicate effectivley via email, such as view and manage your favorite mailboxes right in the Mail sidebar, search for emails, it's easy to see which mailboxes are being searched and quickly select different mailboxes, easily view and sort messages in column layou and quickly open and use tabs in the Mail window.

World's largest secure email service providing end-to-end encrypted email accounts. ProtonMail is based in Geneva, Switzerland and protected by Swiss privacy laws. The software is openly developed with fully open source code.

HEY is a privacy focused commercial email provider. It brings a fresh approach and transforms email into something you want to use, not something you’re forced to deal with.

Microsoft Outlook is a freemium personal email service and email client created by Microsoft. Microsoft Outlook does not scan your email for the purpose of serving you ads. The Microsoft Outlook email client allow you to be productive and stay connected from your home, on the go, and everywhere in between. Microsoft Outlook also integrates well with other Microsoft service allowing you to reach an eco-system of productive apps from within your mail client, be it in the browser or natively on your computer or mobile device.