What about replies that include people who may not have received the original message and its files or replies to people you know will ask you to resend the attachments? The Mac Mail application can make an exception and send complete files rather than text placeholders.
Replace Text File Names With Complete Attachments
To attach the original message’s attachments to your reply instead of using text placeholders in the Mail application for Mac OS X or macOS operating systems:
Open the email that contains the attachment in the Mail application. Click the Reply button without highlighting any part of the text. The attachment is reduced to only a text file name along with the quoted original text in the reply screen. If you must highlight and quote selectively, highlight the desired attachment as well. Select Edit > Attachments > Include Original Attachments in Reply from the Mail menu bar to replace the text file name with the complete attachment in your reply. Add any additional message or information to the reply and click the Send icon.
You can remove the attachments and replace them with text file names again by selecting Edit > Attachments > Include Original Attachments in Reply to deselect the setting.
