Currently only IP addresses or ranges can be blocked. This is partially efficient and I also would want to be able to block email addresses as these can be blocked more effectively.
 
Is there a way to block an email address from purchasing? If not, maybe this can be added?

I'll vote for that, Dick

Aye! I hope there is a way how to block email addresses, and if there is, I want to know about it, please!

are you talking block by domain level or just a single email address?
 
for the email address you could always just create/mangle the "site users/edit user info", and change them to non-approved or a non working user type

i want to block my email address. but i don't know how

ccberries - then they register again with the 'banned' e-mail address?