According to Vice News, the emails were sent after Clinton appeared on NBC News and made a tepid apology for the controversy surrounding her use of a private email server.
"At the end of the day, I am sorry that this has been confusing to people and has raised a lot of questions, but there are answers to all these questions," Clinton told NBC News' Andrea Mitchell on Sept. 4, 2015. "And I take responsibility, and it wasn't the best choice."
>> Related: WikiLeaks emails: Did Clinton say she hates 'everyday Americans'?
Tangen praised Clinton's performance after the interview, but the conversation soured as news coverage surfaced.
"No good deed goes unpunished," Podesta wrote after the interview aired. "Press takeaway was the whine of but 'she really didn't apologize to the American people.' I am beginning to think Trump is on to something."
Clinton called her private email server a "mistake" about a week after the exchange, Vice News reported.
A few days later, in emails dated Sept. 7 and 8, Tanden described frustration over Clinton's lack of an apology, saying that if she emailed the presidential candidate, "she will dismiss it out of hand."
Podesta encouraged Tanden to email Clinton.
"She can say she's sorry without apologizing to the American people," he wrote. "Tell her to say it and move on, why get hung on this."
Clinton's use of a private email server has repeated surfaced as a campaign issue.
FBI director James Comey said in July that despite the fact that Clinton sent and received multiple classified emails on the account,there was no "clear evidence" that she intended to break the law. He did, however, characterize her use of a private server and handling of classified emails as "extremely reckless."