Email address validation of Top Level Domain

Question

Our QA has filed a bug that says top level domain of the email address cannot be of one character.

[email protected]

I am having a hard time looking into standards. Can somebody confirm if setting top level domain minimum length is a right thing to do?

Answer 1

The rules for validating email addresses are as complicated as they are likely to be buggy in their implementation.

Rather than validating an email address, consider verifying it directly instead: http://davidcel.is/blog/2012/09/06/stop-validating-email-addresses-with-regex/

The problem with your case, is that there is a very real possibility that ICANN might introduce single-letter top-level domain names, and individual DNS labels can be of length 1, in fact "bar.z" is a valid email address domain name if sent from within a DNS tree/organization where that exists as a sub-domain (i.e. if the mailserver is smtp.mycompany.org and I've also defined an MX server for bar.z.mycompany.org).

Answer 2

Note that I wrote a small C library call libtld for that purpose. It may be useful to you. Note that the amount of data required to support all TLDs, world wide, is quite staggering so I would not implement such in Javascript. That being said, maybe if you can compress the data more... The library also includes a PHP extension so you can use the functions and results directly from PHP.