Reply to the letter
You can reply to the letter using both "Reply" and "Reply to all" button.
If You are the only one recepient, You can reply straight to sender by clicking "Reply" button:
But If You see another e-mails, whom this letter has been sent, You can write the answer to all there emails at once by using "Reply to all" button:
If you were unable to find answer for your question, please write to email@example.com