Email and face-to-face conversations are the preferred method of communication...

This is according to an Adobe survey of white collar workers with smartphones in the U.S. and the U.K.

There is also a growing corporate concern of using 3rd party apps like Slack and bouncing IP intellectual property and business intel (BP, MP, SP), through a 3rd party. Collaborative team communication and development have book value to farm!  Yeah, like  IP address, device ID, geolocation alarms..... text dumps of analytics to big data.. Phishing/spoofing...  who what when... it’s easier than you think... even hacking a public email account, apparently hacking 500 milion Yahoo email accounts. Yahoo is asking anyone who hasn't changed their password since 2014 to update it. This is good advice for everyone: Passwords should be changed often.   

After the Yahoo hack many companies also are now getting back to taking  control of their own corporate mail server internally and banning FREE email accounts like g-mail for professional business use. Enterprise Firewalls with access logs to email accounts used internally with analytics the company controls. Again, it’s about IP and book value...  MIS, CTO and CFO and Boards   don't SNOOZE on this! 

There is no free lunch, (free email).  Read the fine print of their Terms of Use...EULAs.... “and don't Slack off!!!”  :)