On Fri, Aug 28, 2020 at 10:42 AM, J_Catlady wrote:

I would say that their email address is not their “personal details.”

Not true. Under GDPR (which Groups.io says it is compliant with https://groups.io/static/compliance)   Personal data is any information that can be used to identify someone. It can be something straight forward like an email address or a combination of other things. See https://dataedo.com/blog/what-is-personal-data-under-gdpr for a basic overview.

Andy