Thanks for the explanation. The account I heard said that they left their messages in a draft folder. I’m thinking of OUTLOOK where only the person in possession of the computer has access to the draft folder and furthermore only the draft folder in their own account.
If you have gmail.com mail (or similar), you can compose and read the related e-mails entire online, via your browser. Other than appearing on your display screen, those e-mails never leave gmail.com's server.
Terrorists use the "shared draft folder" method to communicate without actually sending an email. All the network traffic is browser traffic.
Supposedly, the harassing emails sent (supposedly) by Broadwell to Kelly were anonymous / anonymized somehow. If Broadwell sent the harassing communications from the same gmail.com account she used to communicate with Petraeus, well, "stupid" comes to mind, unless she intended to associate Petraeus with the harassment, along with herself.