In Drupal 8, uploaded image files sent to a Webform are uploaded to a private area. The image files are referenced in the email that is sent to the administrator for that form, but unless they are logged in and access the email through the webforms results interface, they cannot see the file. It appears as a broken image in the HTML email.

I've installed SwiftMailer and Mail System modules per https://www.drupal.org/node/2837024 but installing and enabling the modules has not solved the problem.