Domain name geekery

If you’re not technical, there’s nothing to see here. Move along please.

OK, I’m writing an email address validation function. Why? Because everybody else has and why should I be different? The catch is, I’m trying to make it RFC-compliant rather than use the same noddy regular expressions everybody else does.

Ask me anything you like about RFCs 1035, 2396, 3696, 4291, 4343, 5321 & 5322. Go on.

Try this one: RFC 1035 says the following:

The labels must follow the rules for ARPANET host names.  They must
start with a letter, end with a letter or digit, and have as interior
characters only letters, digits, and hyphen.

(A label is a component of a domain name, i.e. the “example” in example.com)

So is 3com.com a valid domain name? No? Somebody should tell them.