The best open source alternative to Zoho Mail is Proton Mail. If that doesn't suit you, our users have ranked more than 100 alternatives to Zoho Mail and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Zoho Mail are Tuta Mail, Disroot, FairEmail and Posteo.
Proton Mail provides secure email services with end-to-end encryption, ensuring data protection. Swiss-based and outside US jurisdiction, it offers a free version to champion privacy as a human right. Fully accessible on any device.
Encryption and secure service.
Offers comprehensive encryption for email, calendar, and contacts with zero personal info required. Built on open source, install via Play Store, F-Droid, or APK, with Tor and VPN support. Both free and paid plans; utilizes quantum-resistant encryption ensuring privacy-focused, anonymous usage.
Free plan does not allow your own domain
Its open source, so its bugs will always be minimal.
Disroot is a platform providing online services based on principles of freedom, privacy, federation and decentralization.
Open-source, privacy-focused email client offering features such as encryption via OpenPGP and S/MIME, unlimited accounts, a unified inbox, customizable settings, and reformatted emails to prevent phishing. Supports two-way synchronization and provides Pro features for additional customization.
Web- and IMAP-based email service. 4GB cost 1€/month. Information is hosted on encrypted hard drives. Electricity from renewable resources is used.
Privacy-focused Swiss email system provides 20 GB free storage, supports custom domains and unlimited storage, syncs contacts and calendars, is ad-free, and is part of a secure productivity suite used by over a million users across Europe on all devices.
Kolab Now provides a suite of intuitive apps in a user friendly environment to make your day to day online comms easier, smarter and most importantly; secure.
Horde Groupware is a free, enterprise ready, browser based collaboration suite. Users can manage and share calendars, contacts, tasks and notes with the standards compliant components from the Horde Project.
Swisscows.email is another product of Swisscows AG. This product offers you secure email traffic. With Swisscows.email you can send your emails encrypted so that absolutely no one can read them. The service is comparable to a letter that is protected from prying eyes in an...
Zero is an open-source AI email solution that gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers. Our goal is to modernize and improve emails through AI agents to truly modernize emails.
Afterlogic Aurora is an enterprise collaboration system for small and medium-sized business. Aurora provides collaboration of webmail, contacts, calendar, files and helpdesk modules.
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Free plan does not allow your own domain