Why is Received Date days later than the Sent Date?

Microsoft's Messaging Application Programming Interface (MAPI) is used by programs like Microsoft Outlook to send emails, and it includes various properties and fields for different pieces of information.
 
Venio typically extracts the following MAPI properties for the sent and received dates:
 

• PR_LAST_MODIFICATION_TIME : This property represents the delivery time of the email, which would typically be the "Received" date/time.
• PR_CLIENT_SUBMIT_TIME : This property represents the time at which the email was submitted by the client to the message store, which is typically used as the "Sent" date/time.

For draft emails, however, received date is not be populated as the email hasn't been sent or received. In this case, Venio instead uses the PR_LAST_MODIFICATION_TIME MAPI property for received, which represents the time when the email was last modified. For sent date, Venio instead uses the PR_CLIENT_SUBMIT_TIME MAPI property.

How the sent and received date are calculated in outlook is described in the following article from Microsoft.