If cookies are disabled, you will be unable to login to facebook. You'll see an error like:
Cookies are not enabled on your browser. Please adjust this in your security preferences before continuing.
To enable cookies:
- Preferences / Advanced / Config Editor on the Mac or Tools / Options / Advanced / Config Editor (on Windows)
- type in: network.cookie.cookieBehavior
- set the value to 0
- and restart Postbox.