Yep and depending on the position starting pay is around $20/hr (for clerks at least, usually less for mail handlers).

You start in a temporary position but they really do want to convert you to a regular position, so long as you're a good worker and make it past your 90 days you're in. Includes health benefits at the start, multiple yearly raises, and once you convert to a regular you get like a $4/hr raise and additional benefits as well as those yearly raises. Protected by a union and dues are minimal. Ability to transfer crafts if you don't like where you start out or get bored, and the ability to transfer states and locations if you ever want to move.

Heads up the hiring process is long and it may seem like they ignored your application for a while. I got lucky with starting my orientation about a month and a half after I originally applied but I've had other coworkers say it took like 3 months.