OK, its clear USPS does not allow customers to re-use priority and other packaging.  But what about other carriers? 

I received a book in a recyled DHL bubble mailer, turned inside out.  Is this kosher, or would it have been a problem if subject to Media Mail inspection?  Haven't logged the book in as received yet, and wondering if I should mention the packaging to the sender?

I am quite sure USPS cannot control other company's packaging.  I've seen plenty of people bring their shipments packaged in DHL, UPS, or FedEx packages to the USPS counter and there is no problem with the USPS clerk accepting the packages for shipping.  I, myself, also use old DHL and FedEx bags and never had anyone comment or bring it up.   Media mail inspection is to inspect the item you are shipping to ensure it meets the requirements, not how it was packaged, with the exception of using USPS packaging.

Thanks Susan!  I'll just log the book in with a nice thank you...and recycle the mailer again!

Last week I was in line at my local Post Office and a customer in front of me had wrapped twine around his package.  Since it was already wrapped in brown paper,  twine seemed redundant...and I thought USPS had banned it's use several years ago as being a hazard to sorting machines?  Unfortunately, the customer changed his mind and left before his turn at the window, I was curious what the clerks would say.

I don't think they care about mailers from other companies although I would block anything that said like Express Shipping or Next Day Shipping or something.  But I reuse envelopes from UPS, FED Ex and others.

I think their main issue with reusing their Priority envelopes and boxes is that they provide those free when you pay for that service. So they don't want people just helping themselves to free mailers and then using cheaper postage.

Denise,

You are right  in your thinking that the USPS had banned using string or twine. Here is that info from the USPS website:

Sealing
Tape the opening of your box and reinforce all seams with 2? wide tape. Use clear or brown packaging tape, reinforced packing tape or paper tape. Do not use cord, string or twine because they get caught in mail processing equipment.
 

http://www.usps.com/send/preparemailandpackages/preparingpackages.htm

USPS doesn't care about other company's mailing supplies.  Just like UPS and FedEx and DHL don't care if  you use Priority Mail or Express mail supplies to ship with them.  Not that I advocate doing that but we certainly receive packages at work in Priority Mail packaging that's sent by UPS or FedEx.

I understand why the USPS doesn't want you to use priority mail supplies to mail something that is not priority.  They don't give away their supplies to allow people who are too cheap to bguy their own boxes to mail something not priority.  But, I don't understan;d why they frown on re-using a priority mail box which is nothing more than recycling. 

I think that could open up a can of worms, Kate. How do they you're re-using it? That could add too much judgement to the process so I guess it makes sense that they just ban them period.

The USPS allows you to reuse priority and express mailers as long as you pay the appropriate postage. 

So wait...the bubbles were on the outside of the package?  I'm shaking my head at the picture in my head...

Yes Karen, looked a little odd.  The backing is gray, with clear 'bubbles' and another clear plastic layer (previously inside) so the surface wasn't too bumpy.