SpamSieve created new Trash folder

I’m trying out SpamSieve for my iCloud account and I found that it created a new Trash folder. I already have a Trash folder but it created another one that now has thousands of spam messages in it. How do I get SpamSieve to use my actual Trash folder?

I would not expect SpamSieve to create a Trash mailbox unless you specifically chose a custom name. Are you using Apple Mail or a different mail client? Is the Trash located On My Mac or inside of your mail account? Does it contain messages that you trained as spam or incoming messages that SpamSieve automatically caught as spam?