I would normally take her word up at our post office, except that this lady proceeded to suggest "Express" mail after I had already specified Media Male because they are books, and this with a very long line behind me.  So I question her sanity anyways.

She informed me that because the box I was shipping was an old box for quarts of oil (the brand of oil hasn't even been manufactured in 30 years), I couldn't use it to mail.

Is this true and if so what other random boxes should I watch for to not use.  I tried finding it under the help links, but couldn't find anything.

Ah! When you use Media Mail you can't have a box with any advertising on it. She was just being strict with you, but right. Just cover the logos with some duct tape or whip out the magic marker.

And never ever ever ever use an old/new/half a part of a tape of anything with/from Priority mail. The recipient will have to pay postage due to get the package. And if they refuse it's destroyed, media mail has no return service.

It wasn't the advertisement (although I will remember that and keep it in mind - they've let me get away with that before but I don't want to do it if it doesn't pass inspection in that one chance in a million).  She specifically said oil and anything flammable.  The boxes from these items aren't usable.  Didn't make sense to me (I know I can't post "flammable" items, but it's just a cardboard box - this statement strikes me as really funny as a Boy Scout posting books in boxes all of which are flammable by my definition ?shrug?).

In general, you can re-use boxes that don't say Priority Mail. However - and I hope someone will correct me if I get this wrong - I think that the box can't state that it contains anything that is prohibited to mail. In other words, if the box visibly says it contains grapefruit, that's fine if you're mailing it parcel post, since grapefruits can be mailed parcel post. If you're mailing it media mail, on the other hand, they might say that the grapefruit box wasn't okay, since grapefruit aren't media. :)

Is it legal to mail quarts of oil? It might well not be, in which case I see the logic in her refusal to accept that box, Media Mail or not. I think the idea is that the post office has to believe the labels on the box.

You cqn use the box but you have to obliterate anything that makes it appear that the box contains anything hazardous.  Either completely black it out with a fat black marker, spray paint over the writing, use opaque/non-transparent tape over the writing, whatever it takes to cover it up so that it cannot be read.

Thanks all, that makes sense.

That's what bothered me most of all, is it didn't make sense when I'm already declaring it non-flammable (aka books and I've answered the flammable/perishible/fragile question).  But truth in advertising (aka what is written on the box makes sense).

Alcoholic beverage boxes cannot be reused in the mail.  If I have one the perfect size, I've learned to completely cover it in brown paper and secure firmly with packing tape.  I've had no problem recycling little food boxes such as Schwan or Ohama Beef, just deface any bar codes and add PBS mailing label. 

If your outer wrapper has any previous USPS barcodes, be especially sure to remove or deface them.

I've used cereal boxes and various other boxes with "advertising" on them to mail media mail with no problem. I don't cover them up either.  You can't use any box that had cleaning products or basically anythign flammable even if it says media mail on the box. Because people lie and say something is media mail when it really shouldn't be.

if its ON the box the post office has to assume it is IN the box...so you cant reuse a box that has things on it that are not mailable.

Here's the actual information from the USPS website about this.  I was once told that I couldn't mail in an old Avon box since it has a code on the side that means it contains aerosols (like perfumes, I guess).  I guess your oil box would have been considered a fuel, or just flammable in general.  Hope this helps!

The Postal Service?s definition of a hazardous material includes many common household and consumer products. These items may not be hazardous during normal use or storage in your home but can present a significant hazard when placed in the mail due to vibration, temperature changes, and variations in atmospheric pressure.

Some examples of commonly-used items restricted or considered hazardous under USPS regulations include:
 

	Perfumes
	Nail polish
	Flea collars or flea sprays
	Aerosols
	Bleach
	Pool chemicals
	Paints
	Matches
	Batteries
	Fuels or gasoline
	Airbags
	Dry ice
	Mercury thermometers
	Cleaning supplies
	Items previously containing fuel
	Glues
	Fireworks

Other items, such as alcoholic beverages (beer, wine, liquor), are not considered hazardous but are prohibited and boxes displaying such markings are also prohibited.

Reused packaging and boxes are only acceptable when all markings and labels are removed or completely marked out so they cannot be read. Regardless of what is actually inside your package, markings or labels for hazardous or restricted materials may prevent your package from being delivered.

was once told that I couldn't mail in an old Avon box since it has a code on the side that means it contains aerosols (like perfumes, I guess).

That would be an ORM-D code

from wikipedia:

ORM-D is a marking for mail or shipping in the United States that identifies "Other Regulated Materials-Domestic". Packages bearing this mark contain hazardous material in a limited quantity that presents a limited hazard during transportation, due to its form, quantity, and packaging.

Consumer commodity is a hazardous material that is packaged and distributed in a quantity and form intended or suitable for retail sale and designed for consumption by individuals for their personal care or household use purposes. This term can also include certain drugs or medicines.

Examples of items classed ORM-D include:

• Aerosol cans
• Automotive batteries
• Perfumes
• Some photographic chemicals
• Lighters
• Small arms ammunition
• Beer
• Drain Openers

Every PO I have ever been in has the large poster  warning on the wall listing the list shared above and with photos of examples of "illegal " boxes ---even my miniature PO that  has a lobby smaller than our bathroom!  It's probably not obvious to people who are there all the time-- we tend to overlook such things!

Yes, and the poster even shows you how to cross the codes and pictures out in the correct way so you can use the box!

LOL: Just goes to show not all PO's were created equal.  My PO still has the sign up advertising for 32 cent first class postage.  They took down the poster specifying the regulations for 4th Class postage shortly after thanksgiving, maybe in part due to me, I asked what the rates were for that class (to see if it matched or beat Media Mail as it was partially for bound reading materials) and was told they didn't use that anymore (given the yellowing and fading on the poster it may have been older than I am?).