Hi @PdM1,
Legal questions are often multifaceted and there are very rarely general answers. They depend heavily on the country, applicable legislation, and data and whether it’s B2B or B2C. You should on any case consult legal professionals to be on the safe side. My reply does not constitute legal advice.
Very generally, you usually cannot share data of persons unless there is a legal basis, which often has to be an explicit consent.
If you want to approach this with out a legal professional, I’d recommend evaluating a one-time email send, asking for confirmation of the recipients for their data to be shared. Anything else would have a very high risk.
Best regards!