This is to avoid users entering wrongly formatted email address but still they can accidentally give us a wrong email address.Example of a correctly formatted email address but still wrong: [email protected][VALID format but does not exist] Above case specifically happens when you take important customer email on phone and you type in the wrong email.
Then a dns lookup is done, to validate their domain.
If the application is going to make use of a basic level of validation, a quick-and-dirty way to handle the situation might be to implement a simple PHP function that performs pattern matching to a standardized email address format, as we have seen many times.
However, when a deeper and more complex validation is required, we should take a look at well-trusted validation classes, such as Pear’s HTML_Quick Form class, or many other validation classes widely available out there.
So is there a QUICK solution to really check the email without sending a test message to the user? 1) the 550 response indicates that the email address is not valid and you have caught a valid but wrong email address.
This code can be on the server and called on AJAX when user tabs out of the email field.