For all the benefits that email undoubtedly provides – like easy, inexpensive communication and content sharing with anyone, anywhere in the world – its use between teams and individuals in the workplace can be cumbersome, distracting, and at worst, a waste of time. Who hasn’t experienced the frustration of “reply all” irrelevant emails, and never-ending chains that bury important content?

No wonder in the new tech trend, then, that businesses are flocking to new alternatives such as Slack, Campfire and HipChat. These platforms, with varying levels of sophistication, are essentially instant messaging and internal chat platforms that seek to make internal communications much more streamlined, trackable and ultimately more productive. To quote one happy HipChat customer, it’s the “company water cooler and work communication in one place.”

HipChat first launched to the public back in 2010, and Campfire launched even earlier in 2006. But it’s newcomer  Slack that is really powering up this new product category. Across a few short months in 2015 alone, Slack doubled its usage to 1.1 million users, and its valuation, to become the market leader in this space. (It should be noted, however, that Atlassian, the Australian company behind HipChat, this week had one of the strongest tech IPOs of the year, suggesting there’s room for competitors to thrive.)

So how has Slack delivered such incredible growth over a short time? As the company founder Stewart Butterfield explains here to Firstround.com, it has been done by appealing to mid-level managers on a team-by-team basis. Clearly this is quite a different sell from trying to get the whole company on board in one shot, or requiring C-level sign off. And cleverly, it also plays to Slack’s functionality of making it easy to create groups and then manage the workflow more effectively and visibly.

Another key element of Slack’s success is its recognition of the need to be wholly customer-centric. Targeting companies on a team basis provides a great opportunity for word-of-mouth marketing, but also puts them at risk of being shut down by negative feedback. By placing huge emphasis on listening to user feedback, especially during beta-testing but also as an ongoing commitment, the company was able to build trust while building a stronger product – an insight everyone can learn from.

With Slack and most of its competitors offering free versions of their services, they’re also potentially attractive solutions for small businesses. Has your company moved away from email for internal communications? Whatever your story, we’d love to hear from you.