KB235358: Multiple emails are sent to the same recipients in a Narrowcast Dynamic Subscription service in MicroStrategy 9.x - 10.x

SUMMARY:
This article describes the behavior of sending multiple emails for the same subscription in a Narrowcast Dynamic Subscription service due to incorrect setup of the Dynamic Subscription report.
 
SYMPTOM:
A Narrowcast email service is setup to send to a dynamic subscription set with 3 recipients.  After the service execution, 3 emails will be sent to the first recipient, 2 emails will be sent to the second recipient, and 1 email will be sent to the last recipient. This behavior is not limited to 3 recipients.  If there were 4 recipients in the dynamic subscription, then the service will send 4 emails to the first recipient, 3 emails to the second, 2 to the third, and 1 to the last recipient, and so on.
In the DELog, the following error may be logged for this service execution:

Unexpected Error in UsersetSent: [Error: 13 Desc: Type mismatch]

CAUSE:
This is caused by the Dynamic Subscription report being used has a metric defined as the Subscription ID.  In a Narrowcast Dynamic Subscription report, the Subscription ID must be defined by an Attribute with an Attribute Form of type Integer (or Numeric).
 
Refer to the following articles for more details:

• KB31224: A service with a dynamic subscription fails to generate emails for any of the recipients and the error "Type Mismatch" shows in the DE.log in Narrowcast server version 9.x
  
• KB10469: What are the data types and formats of subscription information for dynamic subscription sets?
  

 
ACTION:
Modify the Dynamic Subscription report to use an Attribute with an Integer Attribute Form as the Subscription ID instead of a metric.  After making this change, the service should execute correctly sending 1 email to each recipient and will no longer log an error to the DELog.