Control account creation

Hi,

what ways to control account creation does Mediawiki 1.12 provide? I would 
like to have some kind of restriction mechanism, e.g. that sysop needs to 
approve new accounts.

I already tried

$wgGroupPermissions['*']['edit'] = false;
$wgGroupPermissions['emailconfirmed']['edit'] = true;

without success. I can create an account without providing an email and then 
edit any page.

Thanks, Helmut

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