At the beginning of this year, an amendment to Decree No. 194/2009 Coll. on determining the details of the use and operation of the information system of data boxes came into force, which introduces a number of changes for users of data boxes. It will be possible to send and receive bulk data messages of up to 100 MB from and to all data boxes. This applies both to communications with public administrations and to private postal data messages. Furthermore, the possibility of inserting compressed files in ZIP or ASiC container format as an attachment to a data message is introduced. Support for multimedia formats is also being expanded. You can find more detailed information here.