Or if you use M365 then Viva Engage/Yammer can be great! PS. between the two Mastodon will be better, you can fully disable all federation and even have SSO! +

Or if you use M365 then Viva Engage/Yammer can be great! PS. between the two Mastodon will be better, you can fully disable all federation and even have SSO! + setting up a private Bluesky is quite a bit harder