How should I validate an e-mail address?

Question

What\'s a good technique for validating an e-mail address (e.g. from a user input field) in Android? org.apache.commons.validator.routines.EmailValidator doesn\'t seem to be

Answer 1

Note that most of the regular expressions are not valid for international domain names (IDN) and new top level domains like .mobi or .info (if you check for country codes or .org, .com, .gov and so on).

A valid check should separate the local part (before the at-sign) and the domain part. You should also consider the max length of the local part and domain (in sum 255 chars including the at-sign).

The best approach is to transform the address in an IDN compatible format (if required), validate the local part (RFC), check the length of the address and the check the availability of the domain (DNS MX lookup) or simply send an email.