Hi,
I have a case where a user has sent 2 emails on 2 different days to the same recipient but the mails have not been received by the recipient. We also have a Mail Archiving system which is nothing but a simple email id for which we have journaling rule where a copy of each mail sent or received by our users is forwarded. We checked whether the mentioned emails were present in the mailbox but could not find the same.
Similarly we checked Mail Flow delivery report and did not find the mail delivered. However I can see the email in his sent item. I suspect this issue may have occurred a few other times for this user.
The user who has sent the email sent the mail via his Outlook. His Outlook is configured to receive the mails directly to pst file. The 1st thing that came to my mind was whether his Outlook got disconnected the moment he sent the email. The mail may have shown as sent but might not have been successfully sent for delivery. I don't know whether this is possible. This same issue had been brought to notice by another user where he did not receive an email sent to him by another user.
Regards,
Varughese