What is the choice for intra-corporate communication?

Question

Chats

There was a need to replace ICQ with something newer and more functional. At the moment, everyone has different clients (mainly QIP and Miranda).
Skype was dropped immediately because of its "stability" and bulkiness.
Of the advantages of ICQ (in particular, Miranda), which often help:

• Does not require personal identification
  
• The list of users consists only of those who have been added
  
• Chat history is stored locally
  
• Virtually no effect on the operation of the OS
  
• compact look
  
• Detachable chat window
  

There are many options being considered at the moment. It would be interesting to learn about server solutions.

Answer 1

Openfire on the server, the same Kip and Miranda as clients.

Answer 2

Openfire -
Spark server or Miranda 0.8 - client