HelpScout - Help Scout is a simple, straightforward way to provide excellent support
ChatSecure - ChatSecure is a free and open source messaging app that features OTR encryption over XMPP.
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Element.io - Secure messaging app with strong end-to-end encryption, advanced group chat privacy settings, secure video calls for teams, encrypted communication using Matrix open network. Riot.im is now Element.
tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page
ChatIW - Meet and Chat with new friends around the world.