Snail mail doesn’t sound thrilling, but the United States Postal Service is anything but boring. Here are a few facts about the letter carriers in your life.

1. SOME MAIL IS DELIVERED BY MULE. 

How do you get mail to the bottom of the Grand Canyon? By enlisting the help of mules. Each day, mule trains deliver about 4000 pounds of mail, food, supplies, and furniture to the village of Supai. The local Havasupai tribe receives its mail after an 8-mile journey by 50 horses and mules. Since so much of the mail is perishable, the post office where this route originates in Peach Tree, Ariz. has walk-in freezers. 

2. THERE ARE ALSO POSTAL BOATS. 

Meanwhile, in Michigan, a 45-foot mail boat, the J.W. Westcott, has a contract to deliver mail to passing ships sailing on the Detroit River. Legally, the postal service has to deliver mail to all Americans, even those aboard ships. The mail boat pulls alongside larger vessels, which lower down a bucket on a rope that can be filled with correspondence—the custom is known as “mail in the pail.” The boat even has its own special ZIP code: 48222. 

The Detroit River isn’t the only place where you can receive your mail by boat. In Alabama’s Magnolia River, 176 homes on the 31-mile route receive their deliveries from a 15-foot boat that pulls right up to fixed mailboxes on their docks

3. THE LONGEST MAIL ROUTE IS NEARLY 190 MILES ...  

The longest trip a mailman has to make each day starts in Mangum, Okla., where a carrier traverses 187.6 miles every day. In 2013, Bloomberg ran a profile on Jim Ed Bull, the then-72-year-old who was running the epic route. 

4. ... AND THE SHORTEST IS UNDER 1.5 MILES. 

Not every carrier is piling up the daily mileage. The mail carrier in Moody, Ala. has it relatively easy, only traveling 2 miles each day. The USPS says its shortest rural delivery route is Carrollton, Tex., a job that requires just 1.2 miles of daily travel. 

5. THERE'S A STAMP CAVE ... 

Need a stamp? Try looking in SubTropolis, a sprawling excavated limestone mine in Kansas City. Many companies operate out of the underground industrial park, and the USPS has gotten in on the act. The temperature and humidity level 150 feet underground make it an ideal hub for stamp storage and distribution.   

6. ... AND A FACILITY TO DEAL WITH TERRIBLE HANDWRITING.

Ever wonder how the USPS decodes awful penmanship? It calls in the experts. The Remote Encoding Center in Salt Lake City receives the system’s impossible-to-read mail. The center’s 1000 workers there take on every piece of mail that’s too challenging for the automated mail sorters to decipher or is otherwise incorrectly addressed. According a 2013 Deseret News report, these workers can translate a scribbled envelope into legible, usable delivery information in an average of four seconds. 

7. USPS MAILBOXES WEREN'T ALWAYS BLUE.

The postal service began painting its street mailboxes blue in 1971, when it made the structural switch from the Post Office Department to the United States Postal Service. The color of boxes had varied in the century before that, including a stint in drab olive green after WWI thanks to a surplus of paint in that color. 

8. THE CURRENT POSTMASTER GENERAL STARTED AS A LETTER CARRIER.

In February 2015, Megan Brennan became the first female postmaster general in the United States. She rose up through the postal ranks, starting with a job as a letter carrier in 1986. 

9. DOG ATTACKS ACTUALLY HAPPEN.

Dogs actually do attack postal workers. In 2014, dogs attacked 5767 postal employees. Los Angeles was the biggest hotbed of canine attacks, with 74 mail carriers incurring pets’ wrath.

10. THE USPS HELPS CRACK CRIMINAL CASES.

The postal service is skilled at catching criminals in the act—last year, law enforcement seized 46,000 pounds of narcotics from the mail and identified 778 criminals from fingerprints and other physical evidence found in mail.