Slack is detrimental to team communication in several ways, and bringing it to email is a mistake imho. Slack combines the stress and urgency of text messaging with the importance of email. Your Slack becomes a Facebook or Twitter feed - another infinite feed that addicts you to some level. Since it's a chat, the conversations are shallow and disorganized. For example, search never worked properly in Slack for me. Furthermore, synchronous communication has proven poor for wellness and work-life balance.
I know Slack just got acquired and its the hot new thing but email is great as it is - its our ways of using it that need to change.