Blocklist of E-Mail Domains

Problem

Running a shared Nextcloud with a registration possibility is a bit tricky. The biggest problem are the people who abuse the platform to share war propaganda. In 2021 alone, we have already received four abuse reports from Tech Against Terrorism.

In the meantime, the problem was better, thanks to this https://github.com/nextcloud/preferred_providers/issues/15 change.

Now the terrorists have simply switched to throw-away email addresses and can create an infinite number of accounts. I therefore assume that nextcloud.com/signup is being systematically abused.

Feature Request

Since it makes no sense to create an account with a disposable address (anyone can reset the password, because most of this addresses are public) it would be great if we could ban email domains.

My Feature Request: Allow a list of domains that are not allowed to be used.

similar issue: https://github.com/nextcloud/registration/issues/162

The issue names no files or tests; start by tracing the repository's registration flow and configuration entry points, then review the similar registration issue linked in the request. Done means the application supports a configurable list of blocked email domains and prevents those domains from being used for registration.