How X-notifier handles cookies?

Type 'about:config' in the location bar.

extensions.xnotifier.saveCookies

When it is set to 'true', X-notifier's cookies are saved
in Firefox's cookie manager. (default)

When it is set to 'false', X-notifier's cookies are not saved.
They are on memories, while Firefox is running.

After you set (true or false), please restart Firefox.

Tobwithu explain more clearly for what purpose
by saving cookie on Firefox.

Saving cookie on 'Firefox's cookie manager

• X-notifier uses those cookies.
  It means that X-notifier can access webmails quickly without login.

Not saving cookie on 'Firefox's cookie manager

• X-notifier not uses those cookies, only on memories.
  Prevent cookie related problems with other program.