Can 4-n.us receive emails?
No, 4-n.us cannot receive emails because
it has neither an A record nor MX records.
Should you allow users to sign up to your website using the domain 4-n.us?
No, 4-n.us is a throwaway domain and
should be blocked.
How to block the disposable domain
You can use MailCheck's
free API to automatically block throwaway emails.
Read our documentation to get started. No registration required.