By default, images are added inline in Mail, the mail client in Mac OS.
Add a single image as an attachment
- Control-click the image and select the option to view the image as an icon.
Always add images as attachments
- Open Terminal in Mac OS (Applications > Utilities > Terminal)
- Run the following command
defaults write com.apple.mail DisableInlineAttachmentViewing -bool yes
- To restore the default behavior, run the command
defaults write com.apple.mail DisableInlineAttachmentViewing -bool false