eIS seems to be pretty strict about its “no PO Boxes” rule for sales anywhere, including Canada.
Given that PO boxes are the most secure form of delivery, that the postal system is usually the cheapest, and that Community Postboxes are a thing I guess eIS/eISD are another program with benefits for the seller but none for the buyer.
So back to fuzzification.
Instead of John Doe,POBox 123, Station B, Old Crow Y0B 1K0
We could use.
John Doe
Unit 123, NWC Store 491
Old Crow YK Y0B 1K0
Canada
Not exactly a street address, but the program seems to accept that street addresses are often strange looking.