Utter rubbish. Ivans didn't even *buy* the NE. For all that you know some government flunkie left NE copies on Ivan's desk to back their botched investigation.
From page 43 of the Expert Behavioral Analysis Panel report:
"Among the recipients of the first set of anthrax letters was the parent company of the National Enquirer, American Media Inc. (AMI), then based in Boca Raton, Fla. The address of the parent company at that time — the address to which the letter was sent — was the former address of the National Enquirer itself, as listed in the back issues that had piled up in Dr. Ivins' office. One copy of the paper was found in the hot suite."