Caliopen is described as 'All of your private messages (Email, Facebook, Twitter, Instagram etc.) through a single login. A single timeline, a unified contact list and simplified searches to manage all your private messages. Unified message management' and is an website in the Social & Communications category. There are more than 50 alternatives to Caliopen, not only websites but also apps for a variety of platforms, including Mac, Windows, Linux and Android. The best alternative is Rambox, which is both free and Open Source. Other great sites and apps similar to Caliopen are Ferdi (Free, Open Source), Franz (Freemium, Open Source), WebCatalog (Freemium, Open Source) and Ripcord (Free Personal).