Images embedded in forum posts are not sent with notification emails (forced login issue)

Every file and Picture must be addes as Attachment in Forum posts.
If a user would like to add a picture to the text directly (not as Link to moodle), the picture isn´t visible.

Replication steps:

1. Log in as admin/teacher
2. Create a forum
3. Log in as a test student
4. Subscribe to the forum
5. Log out as the student
6. Log in as teacher/admin
7. Create a post in the new forum
   • Add multiple embedded images using the Insert/Edit image button
   • Add an attachment to the post
8. Wait for the posting timeout (default: 30min)
9. Run the cron if not running automatically (email should be sent)
10. Check email sent to test student

Expected result: Embedded images should be sent with email

Actual result: Embedded images become broken images in email