Preprints from any server: the upload form takes a preprint DOI, checked against Crossref and DataCite when submitted (a published article, a preprint already published, or a DOI that does not exist is refused; an unreachable registry fails open and the curation team is told), and the Persistence DOI is linked to it; the DOI route sends other servers to the upload form with the DOI; the exclusivity confirmation is stored on both routes (it never was); the acceptance email says it only when it was confirmed
