Using at.js implementation as a value for mbox3rdPartyId we can send crmID or email address and then profiles in Target would be sitched? Or we can send only crmID?
Any unique identifier, such as an email address, username, or customer ID can be passed as part of the mbox3rdpartyId to stitch user profiles. It should just be an identifier which should be unique for the individual user.
Would recommend you to go through the below article for more details on how to configure and manage mbox3rdpartyId.