email address validation [duplicate]

Answer 1

There are many spam/trash mailers out there (www.spam.la), that allow you to receive mails to any address. Therefore I suggest not to rely on a "valid" email in the usual sense. Maybe OpenID is an option? For just checking for a "valid" format you can maybe make use of existing functionality like filter_var()/FILTER_VALIDATE_EMAIL.

Answer 2

The following regex matches email addresses:

^([\w-\.]+)@((\[[0–9]{1,3}\.[0–9]{1,3}\.[0–9]{1,3}\.)|(([\w-]+\.)+))
([a-zA-Z]{2,4}|[0–9]{1,3})(\]?)$

rashmipandit@gmail.com - VALID

rashmi.pandit@gmail.com - VALID

rashmi_pandit@gmail.com - VALID

rashmi.pandit@gmail - INVALID

rashmi+pandit@gmail.com - INVALID

If you want more complex as per RFC guidelines, you can use this one:

^((([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+)*)|((\x22)((((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(([\x01-\x08\x0b\x0c\x0e-\x1f\x7f]|\x21|[\x23-\x5b]|[\x5d-\x7e]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(\\([\x01-\x09\x0b\x0c\x0d-\x7f]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]))))*(((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(\x22)))@((([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.)+(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.?$

Answer 3

Use this free web service through either a SOAP call, GET, or POST. All you need to do is feed it an email address and it will return a boolean value representing whether or not it's an actual, deliverable email address:

http://www.webservicex.net/ValidateEmail.asmx?op=IsValidEmail