It happens sometimes, when I sign up for a forum or a website that I get told my e-mail address is invalid. It looks like this: [email protected].

Is there any reason why this might be considered invalid?

1 Answer 1


It's probably the underscore before the @ sign. It's not technically invalid, but it's not especially common, and I can easily see that badly written format checkers would flag it as invalid (you're not allowed to have a full stop before the @, so they might generalise that to all punctuation characters).

  • 1
    Aha! That might indeed explain it. Commented Feb 23, 2012 at 14:16
  • Some sites limit your use of the free email accounts, because they can be viewed as throwaway accounts. Commented Feb 23, 2012 at 14:35
  • 1
    @mhoran_psprep: Here in Belgium, I would say the majority uses Hotmail or Gmail. Don't know about other countries. Doesn't seem like a smart move then :) Commented Feb 23, 2012 at 17:17

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