Merde! I was counting on that EUR4k coming through before xmas....

Just kidding! Congratulations on foiling this attempted fraud. I'd like to extrapolate your option 4 by suggesting that the letter was lifted long before it could have travelled with your postie on his rounds.

Vis a vis the efficiency of French banks, perhaps it's the case that due to the large number of strikes, bank workers have had to become ruthlessly efficient on those days where work actually takes place?