Still being spammed hard! (after reading antispam post)

[davidallsop]

Here are my settings: -

Using reCAPTCHA™ Verification
reCAPTCHA™ Theme White
public & private key entered
Allow Multiple Registrations Per User NO
Verify Email address in Registration YES
Require Unique Email Addresses YES
Looked into email banning but most of my spammers use @hotmail or @yahoo addresses.

I am getting 300+ new registrations per day, most posting porn.

Anything I can do? Will my domain be on a spam list, if so is there any way at all of stopping this without having to moderate all members?