org-ql (
https://github.com/alphapapa/org-ql) is also quite good for this kind of thing.
Here is even a database like query to find the heading, and EMAIL property from all the files in a list returned by the function nb-org-files.
(org-ql-query
:select '(cons (fifth (org-heading-components))
(org-entry-get (point) "EMAIL"))
:from (nb-org-files)
:where '(and (property "EMAIL")))
John
-----------------------------------
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803