I was trying to set up users, add users, but their email addresses were rejected:
"Email addresses and domains must be associated with an active Google account, Google workspace account, or cloud identity account"
What's that all about?
Other addresses with similar domains were accepted.. aol.com, yahoo.com, yahoo.co.uk, sympatico.ca
It seems that those specific users do not yet have their email address associated with a Google Account.
Any users accessing Google Cloud must have either a regular Google Account (using their own email address or a gmail address) or have their email associated with a Cloud Identity instance - for example as part of a Google Workspace deployment.
My assumption is that the other users that worked for you already had a Google Account associated with their email address but the ones that have failed do not. You would need to advise your users that do not have a Google Account to go set one up, they can do that here: Google Account signup page
After that you should be able to add them without issue.
Hope that helps, more details here:
https://cloud.google.com/iam/docs/overview#concepts_related_identity
I am currently using a Gmail user so it's strange
its not working please brief in detailed