Link.
Turn off automatic attachment preview in Mail
Mail, by default, provides a preview of attachments in can read, such as graphics and PDF files. However, you can run a command in Terminal to turn this off. Run the following:
defaults write com.apple.mail DisableInlineAttachmentViewing -bool yes
Quit Mail and relaunch it. When you view a message, all attachments will be shown as icons only.
To restore the original functionality,...
