++ All my accounts disappeared after I restart Firefox
``WebMail`` Notifier utilizes Password Manager of Firefox. If you clear "Saved Passwords", ``WebMail`` Notifier accounts will be gone. Don't clear "Saved Passwords".
You can set this option here.
> Tools -> Options -> Private Data\
-> Always clear my private data when I close Firefox
Uncheck this option.
++ I want to check all unread mails in Gmail(including mails that are not in inbox).
Type **about:config** in location bar.
Find **wm-notifier.webmail4.inboxOnly** and set it **false**