Keep an eye on the progress of this
How have you got this set up? For users to be activated by the admin, they only have to register the account. You do the rest of it.
There might be a better way. You could use the Q&A antispam to require a 'code'. If they want to join they just email you and ask for the code. You set the Q&A to be Q: Please email the admin for the code <address> and then A: something like HD(*Y$*FHPW(NON£RO. No spambot can crack that and you can change the code any time you like. They email you, you send them a code, they can then register themselves and be activated straight away with no further work.
You could also extract a list of the addresses from the database.
SELECT user_email FROM phpbb_users WHERE user_type=1
You will need to change the prefix from phpbb_ to yours if it's different. You can find that in the config.php file if you don't know it.