When an editor creates content that is subjected to workflow, the system does not send an email notification to the approver to make that person aware of the fact that new content needs to be approved.

It seems that the code utilized in 4.3 is slightly different in 4.2. Specifically, this might be the problem:

File: /kernel/classes/ezcollaborationitemhandler.php

line number 163 is currently wrong:
$userList = $db->arrayQuery( "SELECT contentobject_id, email FROM ezuser WHERE contentobject_id IN ( $userIDListText )" );

Seems like it should be:
$userList = $db->arrayQuery( "SELECT contentobject_id, email FROM ezuser WHERE ( $userIDListText )" );

This would utilize the proper WHERE clause that is created on the line above it:
$userIDListText = $db->generateSQLINStatement( $userIDList, 'contentobject_id', false, false, 'int' );

Steps to reproduce

1. Create a trigger and workflow that requires a user to approve another users content before going live.

2. Create content by a user that is governed by the workflow.

3. Notice that the approver does not receive email. Also notice in the mail logs that no mail is sent.