@smaffulli: not sure what you have in mind exactly, but if you really just want a segment to works with, “email=empty” is the no-brainer.
But I think I do understand @ascholten 's point: We do want to deliver DWC even on first hit.
Therefore “segment” is the wrong approach, because it can take a while until a user is in any segment.
created a workaround by using non campaign based for anonymous and campaign based for known.
Without having tried, this sounds like a solution to me. @ascholten can you share an example, maybe?
P.S. If you happen to use TYPO3 CMS with Mautic, there’s a deeper integration that lets you implement this logic directly (and natively, w/o JavaScript).