Mail creation system with improved control of print-data downloading

A system comprising:

• a data source device that generates print data for individual pages to be printed;
• a printer operatively coupled to the data source to receive the print data and to use the print data to print the individual pages;
• a buffer coupled to the printer for receiving the printed individual pages from the printer and temporarily storing the printed individual pages;
• a mail-assembling device including a controller that controls operation of the mail-assembling device, the controller operatively coupled to the buffer to determine on a continuous basis the number of printed individual pages in the buffer and operatively coupled to the data source to throttle on a continuous basis the release of individual pages of print data generated by the data source to the printer based on the determined number of pages in the buffer.