I have to do a lot of mailing stuff at my job, I kind of enjoy wrapping unwieldy items that are larger than my whole body and getting them out in the world.
Last month I mailed 7 Murano chandeliers to Dubai and did not break one piece of glass which was totally amazing. It makes me even more suspicious of the woman on ebay who sent me a picture of a broken kitchen bowl I sent her. She would have had to hit it with a hammer to break that thing, but that's a different story.
I found out the hard way, that you cannot mail a floor lamp in one piece. I did it twice and they broke both of them beyond redemption. (especially the 1920's glass parts that were triple bubble wrapped and then tubed and then wrapped again.) How they broke that stuff is just crazy. I did notice the forklift holes in the sides of the box when it was returned to me. What that tells me is, if it is not square, don't try to mail, UPS, or FEDEX it.
You can go to USPS.com and make mailing labels and have your stuff picked up right at your house. Unfortunately, they do not include the cheaper mailing options as media mail, first class, or parcel post on that site. I asked at the post office and they all played dumb.
Imagine a bunch of butch guys in those bad uniforms with bad haircuts (really, I am going to have to do some serious investigation on why postal employees have bad haircuts. Maybe that's what makes them go "postal", they hate their hair!!) Anyway, imagine these guys shrugging and perhaps fooling with their name tags, and denying any knowledge of what is on their web pages.
There is something wrong with that, but I suppose those guys never have to mail anything that does not fit in an envelope.