Like in title, how reliable is this check.
Every single server in the world have their MX record exposed to the world? Or is there a possibility that there exists a server that hides their MX record and even if email will be valid, check will fail.
UPDATE:
I have already checked Symfony documentation and source. I know and I've tested that only emails domain is checked, not the user part. I just don't know how reliable it is. Is it always possible to check servers MX records.
This validator only check if the DNS user in the email is valid for example if you set this email fail@google.com it will be validated even this email doesn't exit.