Just wondering
In this day and age with all the technology going on, are there still places (USA centric) where postal mail is delivered by horseback?
Don’t know if it’s still going, but as of the year 2000, mail was being delivered by mule team to the Havasupai at the bottom of the Grand Canyon by mule train.
Interesting. Thanks for the enlightenment to an off beat question.
According to the USPS.gov “Fun Facts” webpage, it’s still going strong:
I’m going to tease my local post-master about UDM’s (Unusual Delivery Methods).
Thanks to you and the SDMB, I may be able to trip him up enough to buy me lunch. 
Don’t forget that the guys in charge of the mule train ride horses, although the mail itself is carried by mules. Ask your postmaster when was the last time a USPS postal carrier delivered mail on horseback, and if he doesn’t say “This morning”, you win. 
You need to watch the wording if you’re going to make a bet.
The mail is carried by mules. Therefore it was not delivered on horseback. Even if the human takes the mail from the mules and then puts it in the mailboxes, he or she will probably be on foot at the time.
The proper wording is something like, when was the last time the USPS used horses to deliver the mail? That answer would be “this morning.” Unless you’re foolish enough to track the postmaster home and ask it on a Sunday or holiday. 
Heard on radio that the mail to bottom of grand canyon has changed. They don’t take packages down to people now, at least for some people. They still take letters and small stuff.