I think, for any in-game con to work on the player, it would have to be reasonably sophisticated. And there would probably need to be some chance for the player to get some sort of payback, too, if they were prepared to work at it.
If the email system sent players real job offers - go to X, pick up a cargo of Y, take it to Z - then it might be possible to stick some sort of advance-fee scam into that system: a really lucrative contract that requires an advance payment from the player, but with a promise of big bucks when they make the delivery. Except that when the player gets to X, there's no cargo to collect and nobody has heard of the merchant the player was dealing with.
The difficulty is how to fool the player without it just being annoying. The player has no real information to go on, besides what the game gives them: no social experience of the gameworld, no sense of what sort of deals are possible/probable/likely to be scams. And from a gameplay point of view, I think the player would need to have a chance to take revenge, somehow.
It might be possible to tie up a player in something like a Gold Brick scam
. The player is lured to a rock hermit somewhere, told that miners have hit a particularly large lode of gold/platinum, but they're worried about pirates and want a capable ship to get their treasure to market: the player has a "good reputation, can keep a secret", etc. "We don't want to broadcast our location right now, but if you're interested, head towards … [somewhere several jumps away]". As the player gets nearer, the emails keep coming - more news about the size of the find, more concerns about pirates, how long will the player take to get there, what's the holdup?, and so on.
When the player gets to the right system, they're given a location beacon for a rock hermit. At the asteroid, they're greeted enthusiastically by the "relieved miners" and offered the chance to buy a very large amount of gold/platinum at a big discount: the miners "just want it off our hands … there's been a Black Dog pack and escorts cruising around in the last day or so … you know your own ship of course but we recommend you jump out to another system immediately - perhaps [somewhere nearly 7ly away], they have good prices for precious metals". There could even be arguments among the miners, about the size of profit they're giving to the player. Of course, when the player gets their cargo to another station, instead of (say) 8 tonnes of platinum, they find they're carrying 8 kg of platinum, 1 tonne of alloys, and 7 tonnes of minerals.
If the player ever heads back to the rock hermit, by the time they get there it's abandoned - but there might be a clue as to where the fraudsters went with all the player's money.
Another possible scam would be to get the player to invest in a rock hermit that's "hit paydirt
" - or even just offered the chance to buy "the location of a sweet lode of rich rocks". For the latter, the player might turn up and find a dozen other suckers all zapping away at a few (worthless) asteroids, and indeed at each other …
These sorts of scenarios would all necessarily be one-off player missions. I don't think it would be plausible to expect the player to play through these sorts of things more than once.