I might get flamed here but I have sent birds and eggs to NY, NC, GA, FL, IL and CO. NOT once they required NPIP papers from either post office. Yep that was AFTER 9/11 too! At that time I didn't know too much about NPIP stuff but would I do NPIP? I might but most cases, no and it was not cost effective for me to do so nor do I sell often and in large numbers.
There are plenty of non NPIP folks that do ship birds and eggs across the states and never got stopped or re routed back to the sender. I have talked to my good friend who is the USPS state inspector and he said they do not check for paperwork on the birds at all nor do they care that NPIP must be stamped. All it matters to them, is you paid for the postage and in proper box WITH filters such as Horizon shipping boxes, no exceptions. So when he said that, I figured I would go ahead and ship some eggs to CO and a young pullet to NY. Nada, no problems!
In the past year, I was not able to ship birds but can do hatching eggs. Talked to the gentleman at USPS and he said NPIP is not required but as long you can tell them it is hatching eggs, they will be careful with the package. (yeah right, might not be you Decatur USPS but I'm talking about the distribution center employees).
I have NO idea about the enforcement of NPIP in Illinois but do you really think they are checking every box of poultry coming in???? Anyone can put a bogus NPIP number and no one would stop the package and call the center about it. Too much time and money holding up a package.