You will become a slave to mail and parcels. They don't care about you they only care about numbers. You should expect to be a zombie that has no free time. you will not be able to spend time with children, significant others, or family. You only make money from overtime. Management isn't qualified they just have seniority. I suggest you run unless you have no one at all in your life and you live under a rock. You aren't guaranteed a day off and can be worked all 360 days in a row without any days off. I worked 29 days straight without a day off. I was sick with a stomach virus and I had to come to work throwing up & having diarrhea to work a 12 hour day. There is no such thing as sick days. They will work you until you die and then replace you the second you collapse. You can be fired for anything from dog bites to delivering in an unfamiliar area too late. I had deaths in my family and was not given any time to attend services or to grieve. The union doesn't help you at all.
If you like being on the move & can handle continual lifting of packages of varying weights it's a great job, but if you have any difficulty with lifting, or being on your feet 8 + hours a day at times, it's not the best fit.