Picture from mailnotification is lost

[Fischmue]

• Used Zammad version: 2.7.0
• Used Zammad installation source: package Ubuntu 16.04
• Operating system: Ubuntu 16.04
• Browser + version: Firefox 63

Expected behavior:

1. Comment in ticket is created in the webinterface with an image.
2. Email is triggered to send the comment to the ticketcreator. (#{article.body_as_html}
3. Pictures from comment should be shown

Actual behavior:

1. Comment in ticket is created in the webinterface with an image.
2. Email is triggered to send the comment to the ticketcreator. (#{article.body_as_html}
3. Pictures from comment is not visible.
   

Steps to reproduce the behavior:

1. create Trigger-Rule
   
   
2. comment a ticket with a picture, Not as an attachment.