Chronic typographical errors have resulted in the sending of millions of U.S. military emails to a Russian ally.

The problem stemmed from the similarity between the internet domains of the Pentagon (.MIL) and the West African nation of Mali (.ML). Repeated typos caused sensitive information to be transmitted to Mali email addresses. Such information included “diplomatic documents, tax returns, passwords, and the travel details of top officers,” the Financial Times reported.

A Pentagon spokesperson said the military was aware of the issue.

Lt. Commander Tim Gorman claimed emails sent to ML email addresses “are blocked before they leave the MIL domain, and the sender is notified that they must validate the email addresses of the intended recipients.”

However, a contractor managing Mali’s email domain said he has been collecting misdirected emails from MIL email addresses. Mali reportedly now has access to them.

“This risk is real and could be exploited by adversaries of the US,” Dutch contractor Johannes Zuurbier wrote in a letter to the U.S. government last month.

Zuurbier said he collected around 117,00 emails, adding that 1,000 more arrived last Wednesday.

“If you have this kind of sustained access, you can generate intelligence even just from unclassified information,” former National Security Agency head and retired four-star Navy Admiral Mike Rogers told the Financial Times.

Rogers claimed mistakes were not uncommon.

“The question is the scale, the duration, and the sensitivity of the information,” he said.

Pentagon Press Secretary Sabrina Singh told CNN that none of the leaked emails were sent from official Department of Defense email addresses. She claimed the “only thing that went through” were emails from personal accounts.

Singh said that the Pentagon strongly discourages using personal email accounts for official business.

The Defense Department “has implemented policy, training, and technical controls to ensure that emails from the ‘MIL’ domain are not delivered to incorrect domains,” Gorman said in a statement, per CNN.

“While it is not possible to implement technical controls preventing the use of personal email accounts for government business, the Department continues to provide direction and training to DoD personnel,” the statement continued.