A typo frequently made by military officials has put millions of sensitive U.S. emails in the hands of an African country allied with Russia.

The U.S. military uses the email domain name ".MIL," which is sometimes misspelled as ".ML," the registered domain for the nation of Mali in West Africa. Emails intended to reach Pentagon officials, some containing diplomatic documents, tax returns, travel information, and other sensitive details, have mistakenly reached email accounts in Mali when the domain is misspelled, according to a report from the Financial Times.

The issue was first discovered a decade ago by a Dutch internet entrepreneur, Johannes Zuurbier, who has a contract to manage Mali's domain. Zuurbier has warned the U.S. government of the issue and recently increased his efforts as his contract ends this week, after which the information will go back to the Malian government, a close ally of the Kremlin.

"This risk is real and could be exploited by adversaries of the US," Zuurbier said in a letter to the United States, according to the Financial Times.

Zuurbier said he has collected more than 100,000 emails since January to show the United States the magnitude of the problem. He collected almost 1,000 emails in just one day last week. He said there are millions in the system from over the years.

The Pentagon confirmed the problem, saying it implemented controls to stop the misdirected emails from being sent.