That was on Digg's front-page the other day, wasn't it? As part of a bigger article. I remember! I don't mind signing up too much so as long as it's actually worth it. Making me sign up for some trivial and pathetic reason just doesn't cut it with me, and I am often very cautious as to giving them my e-mail address.

Talking of which though, concerning the code, I only check for the basic email structure. I'm not so particular as to craft an extensive regex string because at the end of the day, it could still be a false email address. There is a function called checkdnsrr but I remember having some problems with that. You'll really need to check both MX and A records, as relying on the MX record being present is not a good idea, I found. For whatever reason, I am not sure on the specifics.

The best way is to really enforce users to activate their account. That way at least the email address has to be a valid email address. Whether that's a spam address (such as the notorious mail.ru spam), is immaterial because that's the responsibility for another part of the system, though predominantly that responsibility lies at the fingers of the users and the administrators.

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The man who comes back through the Door in the Wall will never be quite the same as the man who went out.