What are some alternatives?
Trillian - Trillian is a decentralized and federated instant messaging platform that lets your whole company send private and group messages, keep tabs on what co-workers are doing, share files, and much more.
Shift - Shift is the ultimate email client for managing Mail, Calendar, Drive, Slack, Asana, Jira, Evernote, and all your other favourite apps
Jitsi - Open-source video calling and chat platform.
Rambox - Free, open source and cross platform messaging and emailing app that combines common web...
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Station - Station unifies all your work tools in one neat & productive interface.