What's the state of the art in email validation for Rails?

Question

What are you using to validate users' email addresses, and why?

I had been using validates_email_veracity_of which actually queries the MX servers. But that is full of fail for various reasons, mostly related to network traffic and reliability.

I looked around and I couldn't find anything obvious that a lot of people are using to perform a sanity check on an email address. Is there a maintained, reasonably accurate plugin or gem for this?

P.S.: Please don't tell me to send an email with a link to see if the email works. I'm developing a "send to a friend" feature, so this isn't practical.

Solution 1

With Rails 3.0 you can use a email validation without regexp using the Mail gem.

Here is my implementation (packaged as a gem).

Solution 2

Don't make this harder than it needs to be. Your feature is non-critical; validation's just a basic sanity step to catch typos. I would do it with a simple regex, and not waste the CPU cycles on anything too complicated:

/\A[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]+\z/

That was adapted from http://www.regular-expressions.info/email.html -- which you should read if you really want to know all the tradeoffs. If you want a more correct and much more complicated fully RFC822-compliant regex, that's on that page too. But the thing is this: you don't have to get it totally right.

If the address passes validation, you're going to send an email. If the email fails, you're going to get an error message. At which point you can tell the user "Sorry, your friend didn't receive that, would you like to try again?" or flag it for manual review, or just ignore it, or whatever.

These are the same options you'd have to deal with if the address did pass validation. Because even if your validation is perfect and you acquire absolute proof that the address exists, sending could still fail.

The cost of a false positive on validation is low. The benefit of better validation is also low. Validate generously, and worry about errors when they happen.

Solution 3

I created a gem for email validation in Rails 3. I'm kinda surprised that Rails doesn't include something like this by default.

http://github.com/balexand/email_validator

Solution 4

This project seems to have the most watchers on github at the moment (for email validation in rails):

https://github.com/alexdunae/validates_email_format_of

Solution 5

From the Rails 4 docs:

class EmailValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    unless value =~ /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
      record.errors[attribute] << (options[:message] || "is not an email")
    end
  end
end

class Person < ActiveRecord::Base
  validates :email, presence: true, email: true
end

View more solutions

Comments

[Elijah]

Err, won't that barf on .museum and the new international TLDs? This regex would prevent many valid email addresses.

[Jaryl]

Agreed with Elijah, this is a bad recommendation. Additionally, I'm not sure how you think you can tell the user that his friend didn't receive the email because there is no way to tell if the email succeeded right off the bat.

[SFEley]

Good point on .museum and such -- when I first posted that answer in 2009 it wasn't an issue. I altered the regex. If you have further improvements, you can edit it too, or make this a community wiki post.

[SFEley]

Jaryl: There's no way to know for sure if it succeeded or failed, but many failures will send back a bounce message, and you can set up your mail service to tell you about them. You can then make the appropriate notifications to the user or to whomever else ought to know.

[Peter Nixey]

This is exactly the regex I was looking for. At the end of the day as SFEley pointed out, the only thing the validation needs to do is to help the user realise if they forgot to put in an email or entered their name or similar by mistake. If they want to give you an invalid email they will.

[jasoncrawford]

Doesn't seem to work for me in Rails 3.1. Mail::Address.new("john") happily returns me a new Mail::Address object, without raising an exception.

[jasoncrawford]

OK, it will throw an exception in some cases, but not all. @Hallelujah's link seems to have a good approach here.

[jasoncrawford]

Nice, I am using your gem. Thanks.

[Nerdmaster]

FYI, this will still miss some valid email addresses. Not many, but a few. For instance, technically #|@foo.com is a valid email address, as is "Hey I can have spaces if they're quoted"@foo.com. I find it easiest to just ignore anything before the @ and validate just the domain part.

[Rob Dawson]

This is essentially a wrapper around the regex.

[ZoFreX]

I agree with the motivation that you should not worry about allowing through some incorrect addresses. Sadly this regex will disallow some correct addresses, which I view as unacceptable. Perhaps something like this would be better? /.+@.+\..+/

[mjnissim]

Building on the above, put this in your model: validates :email_field, :format => { :with => /\A[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]+\z/, :message => "Email address not valid" }, :allow_blank=>false

[JD.]

Thanks for this snippet, Sam. I'm a little surprised there is not a generic "good enough most of the time" validation provided by the Mail gem.

[pyCthon]

yeah i think the regex as just an example to build upon for your custom needs this works nice for other languages too thanks!

[Lluís]

to allow coma-separated emails: \A[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]+(,[A-Za-z0-9._%‌​+-]+@[A-Za-z0-9.-]+\‌​.[A-Za-z]+)*\z

[cwd]

Can you give an example of how to use this with an if or unless statement? Documentation seems sparse.

[cwd]

looks like ###@domain.com will validate?

[balexand]

@cwd I think the documentation is complete. If you're not familiar with Rails 3+ validations, then check out this Railscast (railscasts.com/episodes/211-validations-in-rails-3) or guides.rubyonrails.org/active_record_validations.html

[Admin]

validates_format_of :email, with: /\A[^@]+@[^@]+\z/ combined with a dns domain blacklist, captcha and actual email confirmation

[Joe Lalgee]

My ultimate email validator: /\A\S+@\S+\.\S+\z/

[Hallelujah]

Guys I would like to revive this gem, I did not have time to maintain it. But it seems people still use it and look for improvements. If you are interested, please write me on the github project : hallelujah/valid_email

[Mauricio Moraes]

I'm tempted to use your validation, but I have no idea where you got it from or how you made it. Can you tell us?

[Dave Sag]

I got the regular expression from a google search, and wrote the wrapper code and spec tests myself.

[Mauricio Moraes]

Its great that you posted the tests as well! But what really got me was the power-quote up there! :)