This is all I have on Sync :

• https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer
• https://support.mozilla.org/en-US/products/firefox/sync
• https://support.mozilla.org/en-US/kb/how-do-i-choose-what-types-information-sync-firefox
• https://support.mozilla.org/en-US/kb/firefox-sync-troubleshooting-and-tips

There is contact info in this and yes do have to create a account and wait :

• https://support.mozilla.org/en-US/kb/forum-response-firefox-sync-verification-email-faq

Please let us know if this solved your issue or if need further assistance.

You can try to log in to the Firefox account via this website.

• https://accounts.firefox.com/signin
• https://accounts.firefox.com/settings

Thank you for your answers. Unfortunately, nothing works. It doesn't recognize my e-mail address. I still get the same message "unknown user". As I read in this article http://mzl.la/1BARU2a, there's no way to recover an email address associated with a Sync account.

Try the contact info in the last URL of the post I made above. Make a account and do what it asks.

Or get a yahoo account and will get disposable addresses also. Start over.

Please let us know if this solved your issue or if need further assistance.