Mr. Grimes wrote back the next morning to apologize.
“David, Sorry. That email was not meant for you. Wrong David!” he wrote.
Mr. Perdue then contacted his wealth manager at Goldman Sachs, Robert Hutchinson, and instructed him to sell a little more than $1 million worth of Cardlytics shares, or about 20 percent of his position, three of the people said. One person familiar with the inquiry into Mr. Perdue’s trades said that the conversation was memorialized in an internal Goldman Sachs record later obtained by the F.B.I.
Financial disclosure forms Mr. Perdue is required to file with the Senate show a Jan. 23 sale of $1 million to $5 million in Cardlytics stock.
Investigators in Washington began scrutinizing Mr. Perdue in the spring; by June, the U.S. attorney’s office in Atlanta was handling the case along with prosecutors in the department’s criminal division in Washington.
Mr. Hutchinson told the F.B.I. that Mr. Perdue and his wife weighed in only on broader investing issues, like the proportion of stocks and bonds to hold in their portfolio, according to a person with knowledge of his interview. But a person familiar with the senator’s money-management arrangements with Goldman Sachs said that Mr. Perdue retained some degree of discretion over which trades were made and when.
In this case, Mr. Perdue’s legal team told investigators that Mr. Hutchinson had advised their client in October 2019 that he needed to sell Cardlytics shares to balance his holdings. The shares had increased in value and the advisers argued that Mr. Perdue should take the profits from the sales and reinvest them elsewhere to limit his exposure to the fluctuation of a single stock. Mr. Perdue elected to go forward with those changes in January, his lawyers said.
Mr. Hutchinson declined to comment.
After conducting interviews, including with Mr. Perdue and Mr. Grimes, investigators reached their conclusion that the senator had no nonpublic information about the company’s performance when he made the Cardlytics trade. The investigation was closed later in the summer, according to the people familiar with the case.
If the email from Mr. Grimes was accidental, said Tai Park, a former federal prosecutor and white-collar crime partner at the law firm White & Case, Mr. Perdue “may be on firmer ground, because that’s objective evidence that the C.E.O. was not trying to tip him. In any event, trading on the basis of information learned from a C.E.O. of a company is exceedingly risky under any scenario and could draw attention from investigators.”