If you are looking for best free group messaging service – Bitrix24 is it. Instant messages, emails, group chats,
private social network, video conferencing, screen sharing, file sharing and even good-old phone calls are all available to you. Again, all of this absolutely free for unliminted members. Unlike other solutions, Bitrix24 is available both in cloud and as self hosted software that can be installed on your server. Open source code access is provided when you purchase on premise license, starting at $1,311.20.
As any business messaging and unified communication platform, Bitrix24 can seem a bit ‘too much’ at first. Please watch these videos
or read Bitrix24 manual if you need help. If you decide to go for the self hosted editions of Bitrix24,
rather than the cloud ones, here are pricing, features and download details.