This is not currently built in, but is not hard to implement as a custom mod. Basically, you could modify the ActivationKeySpammer class to sent the activation e-mail to your forum "registration moderators". They can then decided to click on the activation link (and sent the real user an e-mail) or not.
The message that the user sees can be changed by modifying the User.GoActivateAccountMessage property in the various language file. [originally posted on jforum.net by monroe]
Space seems cool in the movies, but once you get out there, it is super boring. Now for a fascinating tiny ad: