From what I can see, the only sure-fire way around this is to set new users by invitation only. At least you can choose who joins.
If that's too harsh, you can make the core changes below, but you will still have to set the moderation properties in the admin panel to something controllable. Here's my settings (attachment).
Then you will need to ensure that non members can't see a thing. NOTHING. Use your splash page to let them see what the site is about.
Unfortunately Dolphin allows non members to see too much, so you will need to make these core changes offered in a free mod by AntonLV
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This is from a previous post I made:
I wish to thank AntonLV for supplying this FREE routine that fixes everything:
https://www.boonex.com/m/Mandatory_Confirmation
What happens now:
- The person signs up and is advised an email has been sent.
- They can only see the original home page for prospective members.
- If they try to log in, they're told their password is invalid. (Previously, they could log in and see their Profile, Photos and Videos home pages with thumbnails.)
- The person is listed as an unconfirmed member in the admin panel.
- When the person confirms their email address, the receive a "Please Wait" email.
- Admin is shown that the person has confirmed their email and can approve the profile.
- The person receives an email stating that their profile has been accepted.
- They can now log on and see stuff for the FIRST TIME!
These easy changes to four(4) core files take about five minutes and they vastly improve the security of the site All I can say is "Thanks Anton!"
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You will still get spam attacks but at least you can evaluate the email address and decide if it's fake.
I'm getting a few from addresses like io1.a.12.c@gmail.com and their user name and name usually starts with "A" to put them at the top of the list. No sane person has an email like that so just delete their join request. In my case, none have returned.
Good luck. The mods are worth the trouble and please thank Anton.