In the UK it was only the actual Royal Mail (and particularly Parcelforce, their "commercial" offshoot) that actually hold items to ransom. This has always been illegal, something to do with "interfering with the Kings/Queens mail" and was a hanging offence back in the good old days. Unfortunately nobody got hung drawn and quartered in the past century and so they got away with it for a long time. Apparently with the privatisation of Royal Mail they have finally got statute law to give them the unique ability to hold goods to ransom, the commercial carriers don't have that.