(Credit: Astro/Slack Technologies)

Slack seems to becoming the workplace chat app of choice, crossing a threshold of 3 million paying users back in May, with 8 million monthly active users altogether. Facebook, Microsoft, and others keep nipping at its heels, but the platform remains a moving target. For example, Slack has just announced the acquisition of Astro, the maker of Astrobot, a popular email app that had integrations into the chat app.

SEE: Slack competitor Microsoft Teams now has a free preview version

Apparently, the folks at Slack (Android, iOS) were so impressed by Astro and Astrobot's integration that it wanted to snatch up this team before someone else did. In its announcement, the company notes that the developers of Acompli were bought out by Microsoft, who turned it into the basis for Outlook Mobile (Android, iOS); and LinkedIn (Android, iOS) acquired Mumbo.

Astro itself will be getting shut down on October 10, unfortunately, so Slack isn't exactly taking a hands-off approach or attempting to quickly diversify its product offerings. This also means the end of Astrobot for Gmail and Office 365.

It's an unusual move for Slack, because the company has positioned workplace chat as "the main form of business communication by 2025." Color us skeptical, as email can be readily processed offline, tightly encrypted for secure transit, and used to broadcast potentially detailed memoranda.

In order for workplace chat to displace email as Slack predicts, it may have to transform into something that doesn't resemble either communication platform. At the least, it's added a team of 28 people from Astro to help them figure out how to merge the two design concepts -- but that may not be their long-term goal.

Four ways that Slack could leverage the Astro development team

Possibility No. 1: Slack wants to improve the integration of everyone's email services into its workplace chat app. Why just have Astrobot work well, if Slack could connect just as smoothly with Gmail, Outlook, or Yahoo?

And you wouldn't necessarily need to stop with webmail, either. Millions of office workers around the world get business email funneled directly to their laptops and desktops via servers running Microsoft Exchange or other "enterprise" platforms. Instead of you logging into a website to view your email, the email comes to you and is stored on your device.

Gmail may be the default webmail for most people, but if Slack works well with multiple types of email delivery methods, it could help modernize a lot of businesses that are sticking to older tech for one reason or another.

Possibility No. 2: Slack is acquiring Astro mainly to compete in an environment where big players are increasingly coordinating to provide exclusive features. For example, Microsoft (whose Teams app is arguably Slack's biggest competition) acquired LinkedIn in 2016, and the next year it began offering a new tool called Resume Assistant for Office 365.

In theory, acquiring development teams and their products allows the new owner to add more features to their own offerings more quickly than they would if they were producing something from scratch. Since Slack is competing against players with multi-billion dollar pockets, it may need to pay up to keep up. In which case, Astro could be part of a "buy it now before someone else does, and figure it out later" game plan.

Possibility No. 3: Slack launches its own branded email service. This is not as likely, because of the enormous lead of Gmail (Android, iOS) , which has more monthly active users than all other webmail services combined.

Still, it's not a crazy notion. Slack already offers up to one terabyte of cloud storage per user, which we hope would be more storage than any email account will need for many years to come. There are also options for 5GB, 10GB, and 20GB per user, with the 20GB level getting 24/7 tech support and 99.99% guaranteed uptime. So they've got the capacity, and they're already providing premium support.

This third possibility, while the least likely, could appeal to businesses that haven't transitioned to webmail yet and are shopping around for a way to modernize their communication. And if you're a heavy Slack user, what version of webmail would be better than one developed and maintained by Slack itself?

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Possibility No. 4: Slack wants Astro for its data management AI, rather than its email prowess. The Astrobot chatbot is particularly interesting here. With this tool, users of the app can issue voice commands for various email activities, allowing hands-free use or just a way to get things done without having to familiarize yourself with an app's layout and menus.

And one of the critical puzzle pieces for any virtual assistant is the quality of its speech recognition. Astro's chatbot (also named "Astrobot") has a reputation for accuracy, and Apple's struggles here with Siri have shown this factor to be valuable and hard-won currency.

The Astrobot app itself is (was) also pretty good at filtering out spam and prioritizing email that looked important. So the combination of a high-quality message sorting algorithm and high-quality chatbot speech recognition could easily apply to Slack itself.

Granted, Slack already has its own chatbot named Slackbot -- but you can only communicate with it via text. Astrobot could provide a meaningful voice-activated upgrade to this digital helper.

Regardless of where Slack goes next, the four possibilities laid out here aren't mutually exclusive. The end result may be a combination of them -- or something entirely different. But we can tell you that the acquisition of Astro gives Slack a lot of options that it didn't have before, and we're pretty curious to see where they go next.

The takeaways

  • Slack has bought the popular email app maker Astro, an unusual move for a company that pitches itself as the next step beyond email.
  • We can think of four possible reasons why Slack would make this move, and the most likely one is to create a way for everyone to integrate their email services into the Slack platform as well as Astrobot did.

Also see

Tom McNamara is a Senior Editor for CNET's Download.com. He mainly covers Windows, mobile and desktop security, games, Google, streaming services, and social media. Tom was also an editor at Maximum PC and IGN, and his work has appeared on CNET, PC Gamer, MSN.com, and Salon.com. He's also unreasonably proud that he's kept the same phone for more than two years.