The other thing is, we have a smart campaign to capture those junk records, delete them from both SFDC and Marketo. However, we ran into an error "failed to delete sfdc lead: filtered in SFDC". We got the idea is that the sync has a filter prevents any record without an email address from syncing. So if the deletion got failed without an email address, why records able sync to SFDC at the beginning?
Thank you in advance,