Email Validation Rules Explained
Although the Advanced Email Verifier has a very good email validation success rate, it is simply not possible to guarantee a 100% accuracy level due to certain factors that are beyond our control. The level of accuracy you can obtain depend on the inbound SMTP connection policy of the remote ISP or ESP, reputation of the incoming connecting IPs and many other factors.
To save your time and protect your IP address from being blocked, we added rules for certain email addresses and domains that force the program to automatically mark the email addresses as "Bad" or "Unknown" without even trying to validate them.
In this article we give the detailed explanation of why certain email addresses/domains are excluded by the rules and what to do if you still want to validate them.