Ruby Email validation with regex

TL;DR:

credit goes to @joshuahunter (below, upvote his answer). Included here so that people see it.

URI::MailTo::EMAIL_REGEXP

Old TL;DR

VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/i

Original answer

You seem to be complicating things a lot, I would simply use:

VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z]+)*\.[a-z]+\z/i

which is taken from michael hartl's rails book

since this doesn't meet your dot requirement it can simply be ammended like so:

VALID_EMAIL_REGEX = /\A([\w+\-]\.?)+@[a-z\d\-]+(\.[a-z]+)*\.[a-z]+\z/i

As mentioned by CAustin, there are many other solutions.

EDIT:

it was pointed out by @installero that the original fails for subdomains with hyphens in them, this version will work (not sure why the character class was missing digits and hyphens in the first place).

VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/i

This has been built into the standard library since at least 2.2.1

URI::MailTo::EMAIL_REGEXP

Here's a great article by David Celis explaining why every single regular expression you can find for validating email addresses is wrong, including the ones above posted by Mike.

From the article:

The local string (the part of the email address that comes before the @) can contain the following characters:

    `! $ & * - = ` ^ | ~ # % ' + / ? _ { }` 

But guess what? You can use pretty much any character you want if you escape it by surrounding it in quotes. For example, "Look at all these spaces!"@example.com is a valid email address. Nice.

If you need to do a basic check, the best regular expression is simply /@/.