"You've got mail!"

One of the problems created by the geometry drive is that while it permits interstellar travel it doesn't enable interstellar communications, which can only at best travel at the speed of light. This creates a very specific paradigm where outside of well-packed systems ships tend to be faster than radio or laser signals.

It is not to say that regular interstellar communications do not exist at all. Some groups do use long-range coms lasers at interstellar ranges for messages that can wait for a few years but those create a lot of additional problems - the main one being that any laser powerful enough to send a message to another star is also a very adequate anti-ship weapon.

No, really, there are better uses for big lasers than sending mail to another star. Propelling lightsails for instance.

The interesting thing with faster than light travel is that it has created what could be qualified as "the revenge of physical storage". As laser beams or radio signals are way too slow, the main vector of interstellar communications is old-fashioned courier ships that carry messages and data on physical drives - often DNA-based storage, though the revenge of physical storage also caused a true renaissance in handwritten mail. In a way the interstellar society operates under a paradigm that is oddly reminiscent of the early 19th century: short-range messages take a few hours to reach their destination, a few months to reach distant places, and there is no equivalent to telephone or telegraph lines.

Most communes have their own courier service, often carried out by cargo ships, but there are also two public interstellar mail organisations: the centuries-old Interstellar Post Office operating in Communal Space and the Ekumen Communications Network in Eloran space. Both use relay stations and fast drones to create a cheap, long-range network capable of transporting mail across the entirety of Orion's Arm. Finally, priority messages are often carried aboard dedicated picket ships that combine long-range computation systems and efficient fusion drives. The Moon Communes even use a unique and frankly odd ship, the two hundred kilometres long, antimatter-powered courier ship No Time To Stop. There is even a panhuman cooperative organisation dedicated to delivering mail to the most isolated of places: the Astropostale.

Of course, the reliance on courier ships means that any kind of immediate interstellar communications is impossible which kills any attempt at establishing real interstellar stock markets - which is not seen by many as a real loss. Once again, 19th-century logics apply: someone willing to take part in a cooperative on the other side of Communal Space will have to be ready to wait a few weeks. Who cares? Most courier ships carry love letters and books anyway.