Slack, the $2.8 billion startup that wants to kill email, really is reducing work email

When Slack first launched last year, one of its main goals was to reduce interoffice emails.

Its work communications app lets you send messages or files to coworkers, and keeps everything on file, essentially doing a lot of the stuff emails did for intra-office communication. The company's been growing like crazy and investors have been throwing money at it, last giving it a $2.8 billion valuation (it raised roughly $340 million in less than two years launching).

Based on its massive growth, it's not hard to see Slack's effectiveness at work. But now the company has numbers to prove that it's really helping companies reduce email and improve work transparency.

According to a new survey result released by the company this week, Slack users (1,629 paid users, to be exact) say they see an average of 48.6% reduction in email, with nearly 80% saying it improved transparency and office culture. It's also dropped the number of meetings by 24%, while increasing overall productivity by 32.4%, it said.

And that's helping Slack keep up its crazy growth rate. Its updated numbers show it now has 1.7 million daily active users (roughly 5,000 new active users added each day), and 470,000 paid users. Recently, it hit a new milestone too: one million concurrent users connected to Slack at the exact same time.

In order to make it even better, Slack has released a number of new group messaging features this week. On Thursday, it launched something called User Groups where people can quickly send messages to every channel connected under a certain tag (like, @marketing or @sales), sort of similar to how an email alias works.

Earlier this week, it also launched a new group direct message thread that can loop in up to 9 people, allowing people to have a quick private chats with a group of people.

Here's a quick snapshot of how the new User Group feature works: