I sent a letter to Brussels from Brussels, formed in this style:
Attn: <employee name>
<org name>
P.B. <box №> <street>
1030 Brussel
I only added the attn: line to the top. The street probably should have been on the next line. The letter came back 3 months later with this bPost sticker:
“ne reçoit pas/plus le courrier a l’adresse indiquee”
So apparently something is wrong with that address. Whatever the problem, I cannot imagine why it took 3 months for bPost to figure out there was a problem.
The street missing is probably the issue.
About boost, people are using letters less and less, the service is degrading