USPS dead mail just means that the mail is non deliverable mail to an address.
For example if you send a letter to an address but there's nobody there at that address and you have not put your return address on the mail then the mail would be considered dead mail.
With dead mail the USPS workers usually open the mail to try and find who they can send it back too but if not then they destroy the mail when it's not deliverable.
The cost to send a letter in the 1800's was between 10 cents to 15 cents for delivery to 300 miles but later it was lowered to 3 cents.
Before the modern USPS we know today the mail was delivered by the Iron Horse Train.
Then to deliver to addresses the mail carriers used horse and buggy style of mail vehicles.
Mail was also delivered by Pony Express which a rider would ride a pony to deliver mail fast.
The first mail was delivered on April 14th 1860.
Near midnight on April 14, 1860, the first mail that was sent reached its destination and was delivered in San Francisco.
A mailman or mail carrier can refuse to deliver your mail to your address if there's a dangerous situation or the mailbox etc is blocked.
If the mailman notices something that could endanger them then they can refuse to deliver your mail such as if you had a dog that they may seem as a threat to them.
So if you want your mail delivered you must make sure it's safe for the mailman or mail carrier to deliver your mail to you and make sure your mailbox is not blocked.
A mailman or mail carrier walks on average of of 10 miles per day which is around 10,000 to 15,250 steps per day.
A mail man or mail carrier that walks gets some good exercise and is likely healthier as a result because walking is a good workout and exercise.
Most mail carriers work at least 6 days per week for 12 to 14 hours per day.
A mail carrier may start their day in the post office sorting mail for their route as early as 7:00 AM and then sort the mail for a few hours and case the mail and then head out to deliver the mail.
Some mail carriers walk to deliver the mail and other mail carriers drive delivering the mail.
Most mail carriers that walk to deliver mail walk an average of 10 to 15 miles per day.
Walking is good exercise and being a walking mail carrier can keep you fit and active and healthy but you can also get very sore feet and will be tired at the end of the day.
You also have to walk in snow, rain, sleet etc as you must deliver the mail if safe to do so.
The mail carriers that walk is not a job for everyone as if you cannot handle being out in the cold and wind, rain, sleet etc and walk through all that then you're not gonna last long on that job.
Before you start delivering the mail you also have to case the mail which means to sort the mail into slots to designate where it's going.
You usually have to be pretty fast at this.
Also never put any mail into a magazine or something else because I once worked as a mail carrier and had to sort mail and another mail carrier started to put some other mail into a magazine but was told not to do that.