Welcome to NT
That's different. I've not heard of too many people making waves at the USPS these days that don't go to jail, federal jail that is. They're on high alert and a little nervous these days, so be careful what you say in there. Just my immediate concern when I read your post.
There are forms for everything and if you wrote a legitimate complaint with evidence, I'm sure Uncle Sam will look into it for you.
Venting is good. We all do a lot of that. It has some healing properties to it.
You will find a lot of support here. It may help you work through some of your issues. There's lots of info to research. So make yourself at home and look around. There's forums for just about everything.