occupational spam
n. Unwanted or unnecessary messages sent over a corporate email system.
Mr. MacDonald compared the unneeded e-mail to commercial spam, which often comes in the form of solicitations for pornographic Web sites or financial scams. He referred to the internal business e-mail menace as 'occupational spam.' Forwarded jokes and chain letters are the most common problems, he said, as are unnecessary e-mail replies.
—Tim Lemke, “Workers wasting hours on e-mail,” The Washington Times, April 24, 2001
2001 (earliest)
Peek over your cube wall. That mild-mannered person sitting next you might actually be your e-mail nemesis: an insidious spammer who sends out mocking happy faces in response to office correspondence and who always selects "reply to all." That's right, according to an "occupational spam" study released Thursday by IT research firm Gartner, gratuitous interoffice e-mail has become a huge problem.
—Scarlet Pruitt, “Gartner: Beware of business spam,” InfoWorld Daily News, April 19, 2001
—“Growing Numbers Becoming Upset By Bad Taste of Workplace Spam,” Chicago Tribune, February 09, 1998