Slack is raking in the dough, and is now worth more than $7.1 billion. The messaging platform said on Tuesday that it raised $427 million in a new round of funding, CNBC reports, pushing it to a total of $1.26 billion in funding. Less than a year ago, Slack was worth $5 billion. The new valuation pushes Slack into the upper echelons of Silicon Valley's newest tech start-ups.