Is there a way to scan unusual barcodes? I know there are plenty of apps that can read QR codes and standard barcodes.

Does anyone know of a way to scan unusual barcodes, such as ones found on mail trackers or flight tickets, etc? I imagine the encoding isn't encrypted, just obfuscated, so there's probably something out there already that can read the codes. But I haven't found anything on my own.
The Bar-coded Boarding Pass (BCBP) code is common for flight tickets. There could be other codes too, but there doesn't seem to be any app for it yet.

Mails also have different codes. The US seems to be using Intelligent Mail barcode (IM barcode). IMb Reader can be used for this.

Bottomline: there are several possibilities for the codes. You need to check first what code an airline or postal service is using. Then, check if there are apps for it.