"Well, I make a few extra creds handling special delivery mail now and then. When I've been on a route for a while I often end up with a good deal of steady repeat customers too, and it sometimes leads to very rewarding contacts and insider info. Some people like the personal touch, others prefer it for my discretion."
Or in other words, there is the third option, personal message delivery by a trusted private ship owner, like a Trader Captain with a solid reputation. CT made it a 9+ roll to be approached to deliver a private message with an offer of cr20-120 honorarium for the service. Delivery to be made in person to a specific place or person. Such service also serves as an introduction to the recipient as being reliable and trustworthy, assuming of course prompt delivery without tampering (for those of you with larcenous tendencies ).
Beyond that I give a bonus if you are on a regular route and schedule, after you have proven yourself. Very often the recipient will also add a tip of cr10-60 and may have a reply if you are going back the same way.
Makes for some great role playing and a plausible way to introduce the next gimmick (something the player wants) with a little push (deliver this) and pull (here's a few creds for your trouble).