In Outlook 2010 AD environment, can we have the emails that were sent in an Outlook client's secondary email to show up in the sent folder of that email account. Currently they only show up in the primary user's sent folder.

When you add the accounts, you need to select the folders- Outlook 2010 defaults to giving each account their own folder. Go to File tab, Account Settings button. Select the second account then click the change folder and select the folder you want to use.