How to block accounts from being added as a guest to someone else's Teams?

Question

One of our employees just got a "You have been added as a guest to [name] in Microsoft Teams" email. So their email account was added as a guest to someone else's Teams, not the Teams system we use here.

BUT it was a malicious spam group with a highly offensive name trying to sell illegal services. So obviously I'd like to prevent this in the future. I know how to block guests from entering our Teams system but not the opposite. Weirdly, I couldn't find a reference to this problem by searching the internet either. So how do I block our employees' emails/MS accounts from being invited to other people's Teams (as guests) in the future?

Answer 1

In Microsoft Teams admin center > Users > External access, have a look at sections Teams and Skype for Business users in external organizations (block some or all external domains) and Teams accounts not managed by an organization, these might be what you are looking for.

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Please accept as an answer if this was helpful.

Answer 2

Use the Cross-tenant access settings configuration, more specifically the Outbound B2B Collaboration settings. Detail can be found here: https://learn.microsoft.com/en-us/azure/active-directory/external-identities/cross-tenant-access-overview