Email subsystem blocked after upgrade to Joomla 3.2

The mailonline option introduced in Joomla 3.2 lets websites  with email subsystem completely blocked. Even worse, sites owners don't ever know to have a problem.
Since the upgrade procedure doesn't set mailonline, when the mailer reads this value, it should default to "enabled".

issue tracker: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32617&start=0