GDPR Recital 15 states that
Files or sets of files, as well as their cover pages, which are not structured according to specific criteria should not fall within the scope of this Regulation.
I have found an interpretation that claims
This recital seems to imply that unstructured data is not covered under GDPR, and hence is not subject to access requests. This would mean that any unstructured data should not be included in a data subject access request.
Is this a reasonable conclusion for unstructured data such as message bodies in email archives?