This is generally considered as the base practical level of email validation. This level of validation can be easily implemented via a developer component. False Then Response. This is a theoretical level of email address validation. Currently, this is nearly impossible to achieve.
Internet servers run various operating systems, which handle email in various ways.
Additionally, due to security considerations, many operating systems are configured in such a way that specific email account validation is impossible. Although this is theoretically the best, it is functionally impossible to implement. The closest way to implement this method is to send the user an email requiring that he reply in order to become registered for the web site. The bottom line is that any web site that has little or no email address validation is just a victim of lazy developers. These days data is heaping around us at an alarming rate.