disabling spam filter just one mailbox

Hello Community, is there a way how to disable the spamassasin filter just for one mailbox? One of our costumers is running a small email marketing campaign on his domain, and he is processing bounced emails with one of his mailboxes. Recently he has complained that no bounced emails are processed, we have checked the mailbox, and they are all marked as spam. We have tried to apply ACL, or whitelist but since the bounced are coming from different domains it's almost impossible any advices are welcome Thx in advance