We've covered Slack before. As most tech startups are likely aware, it is a market-leading workplace communication platform.

Yesterday, Microsoft launched "Microsoft Teams," an addition to their Office package that provides a very similar service. That same morning, Slack purchased a full-page ad in the New York Times, "welcoming" Microsoft to the space with a full-page "open letter."

In addition to being hilarious, the letter gives great advice for startups, particularly those facing competition from companies with more resources. Microsoft is trying to use its built-in distribution advantage to outcompete Slack, but as Slack's founder, Stewart Butterfield, argues, there's no substitute for years of user experience engineering and customer service expertise. Startups who know their audience and know their market have a built-in advantage.

As Butterfield puts it: "the moral of the story is if you're a large incumbent with many lines of business, it is incredibly difficult to take on a smaller, focused start-up that has traction in the market."

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