Not sure what "code" you received in that email, but adding additional devices to an existing Firefox Account doesn't need any type of "code" from an email. Mozilla never see's your Password for your Firefox Sync Account' there's no way the Sync login server can send it to you. ''If you are referring to the old "Sync Key", which was 26 alpha / numeric characters with (like) 4 or 4 hyphens, that hasn't been used since the Firefox 28 version and that old server was shut down well over a year ago. Not applicable to the current 1.5 version of Sync.'' https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer#w_connect-additional-devices-to-sync See '''#4''' - '''''Enter the email and password you used to create your new Sync account'''''. And '''#5''' - '''''After you've signed in, Sync will start synchronizing your information across all your connected devices. ''''' And the email that is sent regarding Sync accounts in response to a user request require clicking on a hyperlink in each email to acknowledge / approve each "transaction" or change. And the hyperlink is only good for a limited time; can't wait a few hours or it will be invalid. And you can't copy and paste the hyperlink or type it out on the keyboard; there may be non-keyboard characters embedded in the hyperlink. ''Speculation on my part; all I know is that I wasn't able to copy'n'paste or type the hyperlink when I tried - when I had the email open in a different web browser.''