Whitelisting

Why are there thousands of entries in my email whitelist, all of which seems to be spam email addresses?

I use thunderbird and just delete what is in my spam folder, does this somehow whitelist them?

It there a way to blacklist the entire bogus whitelist in one go? It seems like 20 or so at a time is as good as it gets.

Edit

Now, I can't even move them to the blacklist or delete them. Just get a "sorry we are unable to process your request."

It would be nice if Zoho took spam seriously.