These are defined in the Request For Comments documents (RFCs) written by the lords of the internet.
These documents are not rules but simply statements of what some people feel is appropriate behaviour.
It has happened too often to me to get stuck with a ‘form to email’ script.Everything appears right but the email sent by the script never reaches the destination address.A simple copy-paste of a couple of lines of code will provide you the power to verify email addresses real-time, using our REST API.Real-Time email validation API service protects your web forms and prevents unreachable and risky addresses from entering your database.Because clean data always produces best results Sending good emails to bad lists is worse than sending bad emails to a good list.
We've been around the email marketing game long enough to know that even a marginal difference in list quality can result in a major difference in the final outcome.
Of course every list broker will tell you that their list is "double opt in" and "100% clean", but you know better.
Considering you're a seasoned email marketer, you know the cost of sending bulk email to a list full of old, invalid, non-existent email addresses that will generate lots of bounces and cause you and your ESP a lot of grief.
But if your address works then why does it matter if it's invalid?
That brings us onto the most important principle in distributed software.
Read more here.“Contact us” forms are essential for almost any website.