UBB.threads has several built in tools to help you out.Your first question:
1a) Have you tried the built in Stop Forum Spam tool? Report that user and not only does their email address get reported, but also their IP address. If the person is using multiple different email addresses, the IP protection will catch them. But if they are using a VPN or a public/rotating IP address, such as their cellphone, then they will be a bit difficult to catch.
1b) Have you tried Google's ReCaptia? It helps to stop automated registrations -- or to slow down mass manual registrations from different IP addresses but from the same browser session. CAPTCHA helps prevent spammers and bots from registering or posting.
Set it up here:
Control Panel > General > CAPTCHA Settings
Enable it for new registrations here:
Control Panel > Registration > CAPTCHA VerificationYour second question:
This is the first result when searching Google for "spammer email domains"https://www.joewein.de/sw/blacklist.htm
edit: that list is from 2009. You'll need to constantly update your list if you want to constantly block by email address domains. See solution 1, re: Stop Forum Spam. SFS Does that job for you. And its already built in to UBB.threads.