Cross-platform email client providing POP/IMAP support, robust filtering, multiple accounts, and chat. Extendable via add-ons with RSS/Atom, etc.
GTK+-based client offering fast performance, news reading, robust stability, extensibility via plugins, advanced filtering, encryption, folder and contact management.
The Bat! is a secure email client software, built to protect your correspondence against third-parties.
End-to-end encrypted app for email, calendar, and contacts, requiring no personal data, with open source code and quantum-resistant security.
Secure Swiss-based email with end-to-end encryption and zero third-party access. Available across devices, offering a free version to promote privacy.
Delta Chat looks and feels like other popular messenger apps, but does not involve centralized control, tracking or selling you, friends, colleagues or family out to large organizations. "Privacy by Design" has never been more fun.
An encrypted messaging app focused on privacy, supporting texts, calls, photos, videos, files, and group chats, with no ads or trackers.
A secure collaboration app with end-to-end encryption and interoperability across web, desktop, and mobile. Includes chat, voice, and video calls.
Experience instant messaging with remarkable speed and robust security. Join massive group chats or channels. Enjoy free and advanced features.
An open-source decentralized and encrypted messaging app even without internet connection via Wi-Fi and Bluetooth. Messages are stored securely on your device, not in the cloud. Connect directly with nearby contacts - no Internet access is required.
BeeBEEP is a secure network chat. You can talk and send files with all your friends inside a local area network such of an office, home or internet cafe without a server.
The goal of Gajim is to provide a full featured and easy to use XMPP client. Gajim works nicely with GNOME, but does not require it to run. It is released under the GNU General Public License.
Pidgin is a chat program which lets you log into accounts on multiple chat networks simultaneously. This means that you can be chatting with friends on XMPP and sitting in an IRC channel at the same time.
XMPP, or Extensible Messaging and Presence Protocol, is an open standard for instant messaging and real-time communication, allowing for message exchanges between any two entities on the Internet. It's known for its decentralized and extensible nature.
RetroShare is a open source cross-platform, private and secure decentralized communication system. It lets you to securely chat, share photos, videos, and more, using 
OpenPGP to authenticate peers and .
Utopia P2P Ecosystem. Utopia is a feature-rich platform that is specifically designed to protect privacy of communication, confidentiality, and security of personal data. Utopia is a decentralized network, with no central server involved in data transmission or storage.
MailStore Home - A 100% free single-private-user desktop solution
MailStore Home enables you to backup all your email messages from multiple applications and accounts into one secure and persistent archive. Lightning-fast search, one-click backup, powerful export - all informati.
With Free Address Book - Free Phone Book you can note the addresses, phone numbers, mobile, fax, company name, country, city, website address and email addresses of your contacts and partners.
Open Contacts is an advanced address book program for managing contact info of individuals and organizations with relationships. Distributed as freeware, the program was designed for people who need more beyond ordinary address book programs in order to improve dynamic...
The Nextcloud contacts app is a user interface for Nextcloud's CardDAV server. Easily sync contacts from various devices with your Nextcloud and edit them online.
On-premises file sync, universal access, integrated collaboration, real-time communication with privacy and data control focus.
