Some users are not receiving notification e-mails when signing up. On Discourse it shows that the account is created but it’s greyed out, and it shows that the e-mail was sent.
Is the issue on the Discourse side of things or is this on the users side of things? For reference one of the users said they’re using gmx.net as their e-mail provider.
That’s probably the problem. They can check their spam folder. But it could just be silently deleting them. You can see the troubleshooting new email topic.