Converting email addresses of collaborators

Hi community. I am trying to “clean up” my list of collaborators by converting all email addresses from personal or @gmail addresses to our @organizational email addresses. When i delete or remove the collaborator with the gmail or hotmail address, I resend an invite to their organizational email. Some have accepted the invitation but it has their @gmail address listed again. What could be the cause of that?

Maybe the invites are not for the desired email, but for the user account that is logged in when is clicked/accessed :man_shrugging: