An oldie but a goodie: The Case of the 500-Mile Email:

"We're having a problem sending email out of the department."

"What's the problem?" I asked.

"We can't send mail more than 500 miles," the chairman explained.

I choked on my latte. "Come again?"

"We can't send mail farther than 500 miles from here," he repeated. "A little bit more, actually. Call it 520 miles. But no farther."

https://www.ibiblio.org/harris/500milemail.html