Stern wrote in the email, "It is also our understanding that roughly two dozen boxes of original presidential records were kept in the Residence of the White House over the course of President Trump's last year in office and have not been transferred to NARA, despite a determination by Pat Cipollone in the final days of the administration that they need to be. I had also raised this concern with Scott in the final weeks."
"Scott" refers to Scott Gast, another Trump attorney who was copied on the message.
Cipollone, along with his former deputy Patrick Philbin, were designated by Trump shortly before he left office to deal with the issues related to his presidential records.
CNN has not been able to reach Cipollone for comment on the email.
The National Archives has previously said at least 15 boxes of White House records were recovered from Trump's Mar-a-Lago resort in January -- including some that were classified. And in its search earlier this month, the FBI recovered 11 sets of classified documents, including some materials marked as "top secret/SCI" -- one of the highest levels of classification.
According to the source familiar with the matter, there were about a dozen emails and calls over the course of the year as the Archives tried to get Trump to return the presidential documents.
The Archives was aware that White House records management had identified documents were missing even before Trump left office, according to the source.
Furthermore, the Archives was aware of the two dozen boxes in the residence even while Trump was in office, the source said.
But there was no inventory or documentation of what exactly was in those boxes.
Shortly after Trump left office, the negotiations for return of the documents between the Archives and Trump's team began, according to the source familiar. There were repeated phone calls and communications to try to get the boxes back, but to no avail, the source said.
Finally, in January 2022, Trump agreed to return 15 boxes -- not the 24 boxes the Archives were aware of -- that were being kept at his residence at Mar-a-Lago -- boxes that the Archives determined contained classified documents.
This story has been updated with additional reporting.
CNN's Evan Perez and Gabby Orr contributed to this report.