Currently when a Sender sends an email to a recipient in Outlook desktop client, my add-in will first process this email by sending it to a 3rd party app for scanning and verification. After it is verified, the email will be moved to the Outlook Outbox folder to be sent out.
Issue
The issue arises if the Sender sets a Send Delay rule and the recipient is also a registered user of the 3rd party app. When my add-in processes the email, the email will immediately show up in the recipient's repository in the 3rd party app. However, due to the Send Delay rule, the email does not get sent out from Outlook desktop client until the scheduled time. This means the recipient can view the email earlier (by checking their repository in the 3rd party app) than intended by the Sender.
Question
How do I process the email at the scheduled time as set in the Send Delay rule? Do note that Send Delay rule can be changed in the Outbox folder. Also,
Ideally, I would like to handle the event that occurs just before the time the email is scheduled to be sent out from the Outbox folder but I can't seem to find any such event. Both the Application.ItemSend and MailItem.Send events occur before the email is sent to Outbox folder.