I tested "me@example.com" is unknown, I reckon you can add example domain to your regex.
Also tested an iCloud Hide My Email email address created 10mins ago shows undeliverable, which is understandable.
Thank you for providing feedback.you tested "me@example.com", our system connected to smtp server of example domain and waited for response but as response didn't come, it marked the response as "unknown" with reason as "connection_timeout".
Regarding icloud email, we will surely work and try to cover this icloud hide my email functionality.