If you're trying to check whether an email actually exists (not just if it's formatted correctly), you’ll need to go beyond regex and do SMTP-level checks.

I published an API on RapidAPI that does:

• Syntax validation
• MX record lookup
• SMTP handshake to verify mailbox existence (non-intrusive)
• Disposable domain detection

You can try it here:
https://rapidapi.com/thebluesoftwaredevelopment/api/official-email-validator

It’s REST-based, lightweight, and works well in signup flows or lead validation pipelines.