Spam Registrations - Auto-Deleted Accounts Not Activated

[JP 99]

I have enabled tracaccountmanager and tracspamfilter, registration as  BasicCheck, EmailCheck, RegExpCheck, RegistrationFilterAdapter.

ReCaptcha is currently Google - happy to move to KeyCAPTCHA but it's activation emails never seem to arrive.

So, I still get plenty of spam accounts, albeit not activated.

Is it possible to auto-delete such accounts after say 24 hours?

Any suggests to further improve resistance to bot registration would also be very gratefully received.