Mandatory mail was the criminally protected prohibition against using a different type of transport than the postal service for certain objects of transport . The postal service has existed since state post offices existed. The aim was to prevent the Post's contract to supply all postal customers from competing hauliers on the profitable routes from becoming unprofitable. In the meantime, with the loss of the letter monopoly in 2007, the obligation to post has been abolished.
The postal obligation was already converted into a transport reservation by the law on postal services (PostG) of July 28, 1969 . This was laid down in Section 2 (1) PostG old version.