Comment by ironMonkey

Reasons why i don't feel Slack is a true alternative to emails is that with emails you can print it out and validate the nature of the conversation (BCC ftw by the way). With Slack, any person can just in time edit the message which can lead to really crazy situations, given they are rare, but still semantics is what makes win argumens sometimes.

UPD: any messaging platform that forbids editing is the closes to what we have with formal converations.