With Mail on macOS, it’s easy to reply to or forward messages (and it could be even easier with macOS Big Sur this fall – stay tuned). What’s more, if a message contains attachments, you can include them if you wish. This is how:
Select a message from the message list. To include only part of the original message in your reply, select the text you want to include. If you select the top message in a conversation thread, all the messages in the conversation are selected.
Move the pointer over the message title, and then tap Respond button (to reply only to the sender), Answer all button (to reply to the sender and the other recipients), or Forward button (to select new recipients). You can add or remove recipients as needed.
Then add the text. If you included the original message, vertical bars (called citation field) can be displayed next to. You can have the text appear as quotes if you wish. To add quotation fields to the text, select “Format> Quotation Level> Increase” or “Format> Quotation Level> Decrease.” This also changes the citation level where the selected text is displayed. To paste text as quoted text, select “Edit> Paste as Quotation”.
If the original message contained attachments, you decide whether to include them. To include attachments in a reply: Click the Include Attachments button (it looks like a paper clip) in the toolbar of the message window, or choose “Edit> Attachments> Include Original Attachments” in Reply.
To exclude attachments from a reply, click the Exclude Attachments button (it looks like a square with paper clips) in the toolbar of the message window or select “Message> Remove Attachments.” When you are ready, click the Submit button.
If you always prefer to omit the original message from your replies, select “Email> Preferences”, click Compose, and uncheck “Quote the text of the original message.”