As has already been stated, though no-one seems to have grasped it, that Terminal entry changes how you see attachments. If that's all you are concerned about, then fine - but it has no effect on what your receipients see. Some will see images displayed in the message, some will see them as attachments. It depends on how their email client is set up, and there is nothing you can do to influence it.
Thank you for this.
The problem is, it changes everything to attachments, including a logo in the signature for example, not only the attached file. Regards.
The best solution is to use http://lokiware.info/Attachment-Tamer. It solved my problem for good. I was stuck like you regarding the logo in the signature not showing up. With this small app, it will be just like before ;-)