Thanks Clock. How would I distinguish between a report from the sender compared to one from the sender's email provider?
If it came directly from the sender's email provider company, rather than via the sender.
But as Peter has also said proof of delivery is not proof of receipt and acknowledgement by the intended recipient.
If it were me then I would respond with a statement along the lines of "We have checked our mail systems and cannot find any evidence of receiving "the email" in any of the system folders or log files in both current and backup data. Your delivery report is not a reliable indicator of an email either being delivered to, or read by the intended recipient."
