Social Links in the Inspector Pane (Postbox 3 and earlier)
We removed support for Facebook, Twitter, and LinkedIn in Postbox 4. Why?
After logging into Facebook, Twitter and/or Linkedin web services, Postbox will conveniently display links to a user's social network profiles in the Inspector pane of messages that they sent. In order to take advantage of this integration, you must be logged into these services, and have the Inspector Pane showing.
To enable Web Services in Postbox, go to Preferences/Options > Advanced > Web Services and log into each account.
To learn how to use the Inspector Pane, please refer to the following article: