You can now pull Mailer Images into an HTML email or other web content. This is perfect for following up to ensure a recipient got your mailer if they haven't responded yet. Here's an example of how we use this here at Enthusem to follow up after sending a mailer:
We setup our Marketing Automation system's Workflow to automatically send out the above email 7 days after a card's mail date. The email should hit right after the card should have been received.