Validating an email
Most likely she'll say “Oh yes, silly me” and correct it. Sadly, many websites won't let you register an address with a plus sign in it. Occasionally a user might say “Damn right that's my email address. Better register the account before you lose a customer, even if it's not a . This is great for registering with websites because you can see if they've passed your address on to somebody else when email starts arriving addressed to the unique address you gave to the website (e.g. Not because they are trying to defeat your tracking strategy but just because they are crap. There are acknowledged standards for what constitutes a valid email address.These are defined in the Request For Comments documents (RFCs) written by the lords of the internet.Think about it this way: I register for your website under the email address . That’s probably going to bounce off of the illustrious mail daemon, but the formatting is fine; it’s a valid email address.To fix this problem, you implement an activation system where, after registering, I am sent an email with a link I must click.They've copied a broken regular expression from a dodgy website and they are using it to validate email addresses.
Consequently, the people who make email software have often ignored the RFCs and done their own thing.
However, in the real world ESPs accept addresses that are not RFC-valid, and reject addresses that are.
When we built our validator, we did so based on real-world data RFC spec to ensure more accurate validation.
The result of sending an email to a badly formatted email address would be the same: it’ll get bounced. If you really want to do checking of email addresses right on the signup page, include a confirmation field so they have to type it twice.
If your user enters a bad email address, they won’t get the activation email and they’ll try to register again if they really care about using your site. Enterprising individuals will just copy and paste, but what it comes down to is this: if your user enters a bad email address, you shouldn’t make it more of a problem for yourself than you have to.
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They can get ridiculously convoluted as in the case above and, according to the specification, are often too strict anyway.