Does killing a courier and taking there letter mess up anything in the game. Not when they deliver to you in town though. I saw one walking out in thr woods and I attacked him, killed him and took his note. My map updated and now I have I new quest. Will this stop them from visiting me in town?

Yes. Reload and save his life, you murderous lunatic!

Most likely you just earned a black mark on the Mojave Express registry... But that doesn't even matter because we are in Tamriel, so screw it.

I would guess that's the only way to get that quest. So killing him was a good Idea. There's plenty of courier for everyone.

Basically, what happens in the woods stays in the woods... Nobody knows...

Couriers are unkillable

Try pickpocketing first if you feel bad. If that doesn't work, then go ahead and sharpen those knives.

Not the one i killed. I was just messing around in 3rd person looking at the mechanics of how things moved and I slashed him and he was a courier.

Ok now I killed two out in the woods. Both had letters and now I one quest. Something about meeting someone at a certain spot for
Supplies.