I have come across a bug/quirk in Outlook 2013 where it consistently shows incorrect images in emails if the embedded images have the same CID name.
DPA produces emailed reports with the same CID name so Outlook 2013 shows incorrect images. This only occurs if you are using Exchange Cached mode which a lot of people do.
If the DPA system added a unique identifier (GUID or TIMESTAMP) to the CID name then Outlook would show the images correctly.
This is a large issue here with people needing scheduled reports from DPA.
Thanks