Fringe Runner by Rachel Aukes

A system on the brink of galactic war…
An old space captain hounded by arthritis and war memories, Aramis Reyne struggles to make enough credits to feed his crew and keep his ship flying by running mail and supplies to the farthest, most dangerous reaches of the Collective known as the fringe. When he’s offered a no-questions-asked contract to pick up a package, he jumps at the opportunity. But when a warship captain steals the package, Reyne discovers a galactic conspiracy involving military leaders, a secret organization, fringe rebels, and pirates…with Reyne’s crew stuck in the middle.
Now it’s up to Reyne to break the conspiracy wide open. If he fails, the entire Collective is at stake.