How to Disable Mac Mail.app Inline Image Attachments

If you need to disable (or enable) inline images on Mac OS X Mail.app to view them as attachments, here is what you have to do:

Go to Terminal (Applications > Utilities > Terminal) and then type:

defaults write com.apple.mail DisableInlineAttachmentViewing -bool true

But, if you already have that set up on your system and want to go back, just run the following:

defaults write com.apple.mail DisableInlineAttachmentViewing -bool false

After any of the below commands don't forget to restart Mail.app