Has anyone run into this situation? I was sent a PST file from a client who is experiencing this issue. I open the PST and clearly see that there are 2 different emails...both sent at the same time, with the same subject, and the same attachment name (different size PDF files), and to 2 different internal email addresses. These are 2 separate emails. When I ran the Archive Task against the PST, these 2 emails were seen as the same email with the same Message ID, so only 1 was archived and the other was skipped.

The first email is to address1 with attachment size 7kb, and the second email is to address2 with attachment size 25kb. How could EX view both as the same email?