The easiest and quickest solution!
(this is an old post, to see updates please go to homepage)
I've been struggling with OS X Mail app for some time now. The Mail app is fast, simple, quick and fun to work with. It is so much more than the other bloated mail client apps.
However, there is this annoying issue with sending image attachments to anyone who is not using Mail app (gmail, yahoo, outlook, thunderbird,...). The images always end up inlined and the result is that the people who receive my emails get this little tiny image without options and need to do extra work to see the image. Also a lot of those people are not tech savvy so they quickly lose patience and move on. The solution is to disable image inlining.
I've tried every possible combination to disable image inlining with options and defaults but without any luck. Google searches didn't provide much except that other people are having the same problem. As good old Attachment Tamer stopped working there was no other way than to code one.
The solution - Anti Inline Plugin
So.. I have waited for OS X 10.10 (Yosemite) hoping that this annoyance will go away. It did not. I finally ran Xcode and wrote this tiny plugin that forces images not to inline.
I can again, finally, just drag and drop images to the email with no worries, yippie!.
If you get into trouble I will gladly assist - just drop a note in the comments section or via email (firstname.lastname@example.org).
Also, I have only tested it on Yosemite so I would appreciate feedback on any older OS X versions, thanks!