First, open the email that contains the original text you want to quote in your response.
Select the text you want to quote and click the “quote” feature in the formatting bar. This will add quotation marks to the selected text and indent it to the right.
Write your response below the quoted text. Make sure to clearly indicate that the text you are quoting is from the original email by using phrases like “As mentioned in the previous email” or “As you stated in your email”.
For those emails from somebody, you may want to star them automatically.
You could send out emails using a different ‘From’ address, the one other than your current Gmail account.
These emails are important, and should not be put inside promotion tab!