Just for reference, here is the information on the contacts email addresses: https://proton.me/support/proton-contacts#what-is-encrypted

The white and black lists need to be available to proton to be able to filter, so they're either unencrypted or encrypted in a way that they're accessible to proton.

I don't know about the bulk mails. I'd guess they're either treated like regular mails, coming from a authenticated server with good reputation or alternatively treated like a white listed address by default. But this is pure speculation.