Special Counsel Robert Mueller has obtained “many tens of thousands" of Trump transition emails, including emails of Jared Kushner, transition team sources tell Axios.

Trump officials discovered Mueller had the emails when his prosecutors used them as the basis for questions to witnesses, the sources said.

The emails include 12 accounts, one of which contains about 7,000 emails, the sources said.

The accounts include the team's political leadership and the foreign-policy team, the sources said.

Why it matters: The transition emails are said to include sensitive exchanges on matters that include potential appointments, gossip about the views of particular senators involved in the confirmation process, speculation about vulnerabilities of Trump nominees, strategizing about press statements, and policy planning on everything from war to taxes.

“Mueller is using the emails to confirm things, and get new leads," a transition source told me.

How it happened: The sources say Mueller obtained the emails from the General Services Administration, the government agency that hosted the transition email system, which had addresses ending in “ptt.gov," for Presidential Transition Team.

Taking fight public: Charging "unlawful conduct," Kory Langhofer, counsel for the transition team, wrote in a letter to congressional committees Saturday that "career staff at the General Services Administration ... have unlawfully produced [transition team] private materials, including privileged communications, to the Special Counsel's Office."

The seven-page letter, obtained by Axios, says: "We understand that the Special Counsel's Office has subsequently made extensive use of the materials it obtained from the GSA, including materials that are susceptible to privilege claims."

"We understand that the Special Counsel's Office has subsequently made extensive use of the materials it obtained from the GSA, including materials that are susceptible to privilege claims." The letter says this was a violation of Fourth Amendment protections against unreasonable search and seizure.

against unreasonable search and seizure. "Additionally, certain portions of the [transition] materials the Special Counsel's Office obtained from the GSA, including materials that are susceptible to privilege claims, have been leaked to the press by unknown persons."

The Special Counsel's office said: "We will decline to comment."

The transition sources said they were surprised about the emails because they have been in touch with Mueller's team and have cooperated.

The twist: The sources say that transition officials assumed that Mueller would come calling, and had sifted through the emails and separated the ones they considered privileged. But the sources said that was for naught, since Mueller has the complete cache from the dozen accounts.

Editor's Note: This story has been updated with details from the Langhofer letter to congressional committees.

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