If you go to
Administration Panel > General > User registration settings > Allow e-mail address re-use and set that to no, users wont be able to register using the email address of another member. So, if you ban someone, there email address can't be used again. Likewise, you can set that to yes if you want people to be able to reuse email addresses.
Also, if you go to
Moderator Control Panel > Banning > Ban e-mails or
Administration Panel > Users and Groups > Ban e-mails, you can ban email addresses there. That gives you more options, because you can use wildcard matching to, for example, ban emails that use certain domains (i.e. no emails from
gmail.com), or ban any email that contains the word spam.
Keep in mind, though, that spammers usually just create a new email address, and that they don't usually reuse them. This will more likely stop real people, who usually are too lazy to create another email adress.