Is the spam filter installed as a plugin for email clients or does it run on a mail server?
If it's for email clients you should be able to use it with any existing email accounts.
If it's for mail servers, I'd register a new domain, start using it to sign up on a bunch of internet sites and newsletters etc and the spam should start flowing soon enough.
You'll need to make sure the addresses you want spammed are posted publicly on a few sites too so the scrapers can find them.