Outlook prevents the automatic download of pictures in email messages as a security measure to help prevent possible spamming. It permits images from sites in your Trusted Zone to show but blocks all others. You can override this feature by following this tech recipe:
1. Open Outlook 2010.
2. Go to the Ribbon and select File.
3. Click Options.
4. In the left pane, select Trust Center.
5. Click the Trust Center Settings button.
6. Select Automatic Download from the left pane.
7. Uncheck the Don’t download pictures automatically in HTML e-mail messages or RSS items checkbox.
8. Click OK.
9. Click OK to close the Outlook Options window.