Are you ready for it?

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I kid you not. That is the 4249 character (!!!) regular expression used by the Swift Mailer library to validate an email address.

That is just plain stupid. It is incredibly slow, impossible to understand, and in 99.99% of cases a much simpler expression would be fine:

/^[a-z0-9-_\.+]+@[a-z0-9-]+(\.[a-z0-9-]+)*$/

The other 0.01% of cases are where you tell the user to stop being silly and get a real email address.

Don't get me wrong. I think Swift is a nice library, and it is developed by Fabien Potencier, the lead developer of Symfony (which I love). But really, there are times where developers need to say to themselves, "This is silly; I don't need to accomodate EVERYBODY".