Found the doco for MediaWiki’s email settings and now my config looks a little like this:

$wgEnableEmail      = true;
$wgEnableUserEmail  = true; # UPO

$wgEmergencyContact = "pcwiki@progclub.org";
$wgPasswordSender   = "pcwiki@progclub.org";
$wgNoReplyAddress   = $wgEmergencyContact;
$wgPasswordSenderName = "ProgClub wiki";