Not an AIBU, more of a WWYD.
I live in a ground floor flat. There's one flat above mine and we share a communal front door. There are more flats but they use a separate front door. Their front door is right next to ours. There is no clear numbering on the doors, the postman often gets our post mixed up and puts them through the wrong doors. The landlord lives in the flat next door to us, so through the other communal door. Multiple times he's received our post and has opened it. After he opens it he always brings it round, but he tells us what the letter says so he reads the whole thing. He says he didn't know it was ours.
We've over paid a utility company just short of £100. He has knocked on our door to say he has opened our post and we've received a cheque of the expected amount from said utility company. He didn't bring the post round. I asked where the cheque was. He said he will bring it round when he has the time. I have no idea why he couldn't bring it round when he come round, I didn't challenge him on it.
Wwyd? This is becoming more regular and he's becoming quite reluctant to hand over the post!