Sorry if it repeat theme, but I can't find something same.
Core of idea - Game chat must have different properties on different distance.
I think we need 4 levels of distance.
1) Close distant (0-5km) - everyone can read and send massage, and every one can read this. Massage will be send full and immediately.
2) Low distance (5km - planetary system) - Massage can send only from ship, but player can read when out of ship. Massage will be send full and immediately.
3) Medium distance (star system) - Massage can be send and read only from ship. Massage will be send full and immediately.
4) High distance (between star systems) - Massage can be send and read only from ship. Massage will be send with "lags" (ex.: 1 light year - 1-3 sec) and can be randomly damaged (short massage have more resistance for this, but if it damage u have chance for fully unreadable massage, long massage have lower resistance for damaged, but more word can stay normal).
It must work with public and private massage (except mail - it must have very low speed, but it will be invulnerable for damaging).