In Qlik NPrinting 16 all reports generated in a single task for a specific user are grouped in a single email to improve performances. Sending a single email requires only one connection to your SMTP server instead of open and close a connection for each email.
There is not an option to force to create a single email for each report. The only solution to send a different email for each report is to create a different task for each report. You can clone the original task and leave a single report for each task.
Evaluate also the idea to deliver reports to a shared folder instead of send them via email if the recipient is internal.