US Postage Paid On Demand?

Obviously this is not a stamp, but still an interesting piece typical of today's mail. Has anyone seen this type of corner imprint for a piece of junk mail?



Never heard of US Postage Paid "ON DEMAND". What does that mean? Does the USPS have to keep tract and bill the company? Seems a bit odd to me, especially for a company like General Motors.

I'd be interested to know if anyone has any information on this.

Guess:
I think it is prepaid postage which accrues on account
as the mail is processed and at a certain value, the PO requests payment
which is guaranteed.

I suspect it is the name of this mail services company (in Michigan).




http://ondemandmailservices.com/home/

Thanks for the link. Never knew there was an "On Demand" Mail Service. It certainly explains the corner imprint, though.