The September 4 email was sent during the final stretch of the 2016 presidential race — two months after the hacked emails of the Democratic National Committee were made public and one month before WikiLeaks began leaking the contents of Clinton campaign chairman John Podesta’s hacked emails.

The email came less than three weeks before WikiLeaks itself messaged Trump Jr. and began an exchange of direct messages on Twitter. Trump Jr. told investigators he had no recollection of the September email.

Congressional investigators are trying to ascertain whether the individual who sent the September email is legitimate and whether it shows additional efforts by WikiLeaks to connect with Trump’s son and others on the Trump campaign.