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Rambox gives you the possibility to add common services many times you need, all in one place. It's perfect for people who work with many services for business and private accounts.

Empathy is a messaging program which supports text, voice, video chat, and file transfers over many different protocols. You can tell it about your accounts on all those services and do all your chatting within one application.

Miranda IM is the smaller, faster, easier instant messenger with support for multiple protocols. Designed from the ground-up to be resource efficient while still providing a rich feature set, Miranda includes support for AIM, Jabber, ICQ, IRC, MSN, Yahoo, Gadu-Gadu and more. Additionally, with the choice of hundreds of plugins, icons, sounds and other content.

Chat everywhere! IM+ is the most widely used mobile IM app! Connect all-in-one to MSN, Yahoo!, Google Talk, AIM, Jabber, ICQ, Facebook, MySpace and Twitter on ALL popular mobile platforms.

What does it do:

Kopete is an instant messenger supporting AIM, ICQ, MSN, Yahoo, Jabber, IRC, Gadu-Gadu, Novell GroupWise Messenger, and more. It is designed to be a flexible and extensible multi-protocol system suitable for personal and enterprise use.

dialog app is built and designed for corporate communication on all types of mobile devices - tablet, mobile phones etc.

A simple & beautiful app for Facebook Messenger.Chat without distractions on any Operating System.

qutIM - free open-source multiprotocol ( ICQ, Jabber/GTalk/Ya.Online/LiveJournal.com, Mail.Ru, IRC )instant messenger for Windows, Linux, MacOS X, OS/2, Symbian, Maemo/MeeGo, Solaris and *BSD.

Group messaging platform owned by Microsoft. It's absolutely free, whether you're talking to a group of friends, or texting with one person. Best of all, it works on nearly every phone, via push or SMS. With GroupMe, it's easy to reach anyone, anytime, anywhere.

Sameroom helps connect chatrooms (even when they’re running on completely different services).

Cutegram is a free and opensource telegram clients for Linux, Windows, OS X and OpenBSD, focusing on user friendly, compatibility with desktop environments. Cutegram using Qt5, QML, libqtelegram, libappindication, AsemanQtTools technologies and Faenza icons and Twitter emojies graphic sets. It's free and released under Telegram Messenger is a cross-platform instant messaging system whose clients are open source and servers are proprietary software. Telegram users can exchange encrypted and self-destructing messages, photos, videos and documents (all file types are supported). »