Fedex Smartpost?
 

Anyone have any experience using them?

Seller shipped me an item, tracking shows it was delivered to my local PO, who are supposed to do final delivery, but the tracking has stopped. I entered the tracking in USPS website and says "invalid number" Does USPS track it at all?
Its been two weeks and my PO can't find the package.

The auction said Priority Mail but he sent it Fedex Smartpost instead, when I contacted the seller he offered no help at all. I'm thinking about just filing a claim and be done with it.

I believe when I've received packages that way there was a corresponding and valid USPS tracking number.

I contacted Fedex and they told me to add a 9 in front of the Fedex tracking # to get the USPS tracking # and it worked, I still do not have the package but I was able to put a trace on it.

Not sure if this works for every package.