Bug: your site does not accept some valid email addresses

Summary: The character "+" is valid in email addresses!

This is the content of an email message I sent to United (the airline) about 2 years ago, since I couldn't create an account using a perfectly valid email address containing a + in it. This has been happening with other sites, so I'm posting it here so that I don't need to copy/paste it all the time. And if others want to link to it, feel free!

Edit 11/10/2011: Look at this good link resuming the issue around email regexes, with links to the RFC and some nice examples of "weird" email addresses.

Edit 15/04/2015: Update with new Google help page URL.

PLEASE FORWARD TO YOUR TECHNICAL SERVICES

Hi,

I wanted to point you to an error in your forms all over your site. It is not possible to use email addresses that contain the symbol "+", such as toto+united@gmail.com

Please forward this message to your web development team, as what follows is a technical subject.

A plus is a totally valid symbol in an email address, and is used by Gmail to provide email address alias.

Please update your regular expressions so that it accepts email addresses that contain the symbol "+". This should be done (at least) in your regex on http://www.united.com/ual/asset/err_myprof.js line 937:

var emailRe = /^[a-zA-Z0-9._-]+@([a-zA-Z0-9.-]+.)+[a-zA-Z0-9.-]{2,4}$/.test(chkVal.value);

include a plus in [a-zA-Z0-9._-]

It might not seem very important to you, but once you get the habit of using aliases to filter your mails to different labels (I have just created a special "United" label to store your emails), having sites that say "your address is not valid" when it is is really frustrating.

Let me say it once again: a plus sign in an email address is valid, so don't say it's not!