pages 160-162 of MGT Core:
Mail
Mail is a special form of freight, consisting of large data storage drums which contain a vast amount of information that must be transported from one world to another, but is not vital enough to be entrusted to the X-Boat service or a private courier. To determine if there is mail available, determine the applicable Mail DMs, then roll on the available mail table.
The lack of FTL communication is important especially when it says data storage drums, not parcel and letter bins.
Also, fundamentally, the primary limitation on governance is time to react; historically, no govenrment survived as a single entity past 6 months round trip...
as communication speeds increased, central-authority has been increased across the board... FTJ comm could impact the generation of Governments.