I raised this question on other thread, but it is probably best seperated out into its own topic:

I use Endicia online postage service for my business, so I have been using that to ship my PBS books. I have yet to include tracking/DC, but I am seriously considering it for any future book I might ship. Will my tracking and DC info from Endicia hold as much weight as the DC with the PBS offered postage service?  I don't care about instant credits.  I just want to make sure my packages are getting where they are supposed to and that I am getting the credits coming to me.  It is a hassle and an inconvienience to use the PBS postage when I already have Endicia. But, if PBS doesn't give other tracking and DC info the same weight as their own postage service, then it would be a waste of money. 

No, PBS will only give guaranteed credit for the PBS-DC. The fee paid on the postage service is what covers the credits given out when the guarantee is used. Without collecting the fee, there would be no way they could cover the credits.

It does say in the Help Center that if a member has a delivered scan on a DC and the receiver isn't answering PMs or marking it received they will look into it and it gives you a way for the USPS to track the book through their system to recover it, but in the end it will still depend on the receiver getting the book and marking it received for you to get your credit.

Thank you. It is good information to have.

Just keep in mind that a "delivered" scan doesn't necessarily mean a book has been delivered to the right place.  I have one that went lost enroute to me that shows scanned as delivered but I have never seen the book.