Hope this helps you to decide if the email was valid: * I attached how a non scam "Confirm new sign-in to Firefox" email looks like (drew over my email addresses and IP address of course) * It comes from "Firefox Accounts <[email protected]>" . * The blue button "Confirm sign-in" links to https://accounts.firefox.com/complete_signin?code=###&uid=###&service=sync&resume=###&utm_source=email&utm_medium=email&utm_campaign=fx-new-signin&utm_content=fx-confirm-signin (The ### is replaced with numbers and characters) Mine doesn't tell me to reply to it though, so I assume this is not identical to what you got? What is the sender in your case? What email address do you see when you hit reply to write the response?