Be certain the FBI has done that, maybe weeks ago.
Also probably has seized any/all commercial email accounts of everyone they believe involved.
And by now they are following up on every address in/out, reviewing content and following up on all the traffic in/out of those 3rd parties.
They MUST determine the extent of the leak of Top Secret information...not just the email, the information.
This may take months but they WILL know.
...This may take months but they WILL know....
I hope you are right, but how much pressure will the White House put on the FBI to limit their investigation?