Guest Account Invite Issue

Problem

Recently, one of our users got this error while inviting a guest to our tenant:

Please configure B2B collaboration settings correctly and troubleshoot first, “https://aka.ms/b2b-troubleshoot". Error from Entra B2B: At least one invitation failed. Error: ResponseStatusNotOK, message: Group email address is not supported.

Looks like a tenant-wide issue, right?

Solution

There isn’t one - distribution lists cannot be invited as guest accounts.

Afterword

The admin sees a clean, simple message directly in Entra ID under Invite External User - the user gets a wall of text.