Teams, Microsoft's Slack-like, IRC-like, collaboration tool, picked up an important new feature today: guest access. While announcing the new feature, Redmond also revealed that in the six months since launch, the product has grown to be used by over 125,000 organizations each month.

We asked how many individual users there are, but Microsoft said it had nothing to share on that front.

When it debuted, Teams had a big flaw when compared to Slack—it was only for Office 365 users. Each organization's Teams chatrooms could only be accessed by people who were part of the organization, essentially individuals with an account in the organization's Active Directory. This left these chats off-limits to, for example, contract workers—people outside the organization who were nonetheless collaborating on projects.

To address this, Microsoft is adding "guest access" to Teams. Administrators can now add accounts from outside an organization's users, giving them the access they need. Initially, this guest access will still require some kind of Azure Active Directory account. That means guests will need to be using one of Microsoft's commercial cloud services—typically, their own Office 365 subscription—they just won't need to belong to the organization they're getting access to. At some unspecified point in the future, this feature will be extended to work with any Microsoft Account, opening it up to free users.

Microsoft hasn't yet committed to opening Teams up to non-Office 365 organizations. One way in which Slack has gained considerable mindshare is that it's available to use for free (albeit with certain limitations), making it an option for groups such as startups (who don't want to pay for anything if they can help it), open source developers (in much the same style as they might use IRC), or just groups of friends who want an online space to hang out. Even with guest access, Teams still doesn't enable that kind of ad hoc use. There must be a paying Office 365 organization to create a given Teams workspace; guests are added individually. We wouldn't be altogether surprised to see this requirement lifted once the Microsoft Account support is in place.