Which corporate messenger/chat should you choose?

Question

Messengers

Actually, the question is in choosing a chat, then I will give suggestions for it:
1) Installation on your server
2) Work in a local network without access to the Internet
3) File transfer
4) Image transfer
5) Audio / video calls (the presence of a conference will be a huge plus)
6) Availability of clients under Windows, Linux, Android, web
7) Fully localized
8) Availability of general / private chats
9) Free)
10) For 5-10 active users
11) Multi -login
12) Ideally, send an invitation to an unregistered interlocutor as a link to the web .
13) History stored on the server
14) It is desirable that the server part be installed on Linux.
Help with the search and / or share your experience, thanks.

Answer 1

jabber
but slack is much better