I am writing you since my searches have not lead to something functional yet.
The objective is to invite someone whose email adress is not recognized by Teams (@labaume.finance).
The thing is that I am able to add members with "normal" domain name such as gmail for instance, but cannot add people working at LaBaume Finance.
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You can try adding them as a guest in Azure AD first: https://docs.microsoft.com/en-us/azure/active-directory/b2b/b2b-quickstart-add-guest-users-portal