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Slack's big selling point is that it replaces those lengthy email chains that send shudders down the spines of many workers. Its competitors include collaborative software such as Convo, Fleep, Glip and Cisco Spark. The service now boasts more than 1 million daily active users and the company is valued as high as $2.8 billion.
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Launched in August 2013, Slack is a collaborative messaging tool that allows workers within a company to chat in groups, work together on projects and search previous correspondence.
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