Hi David ITA,
Is this user doing this mailing on purpose, or is this unusual/unexpected behavior on that computer? If it is unexpected then the computer is likely infected and part of a spambot. Locate and remove the malware responsible!
Using Today's SymHelp to Combat Today's Threats
https://www-secure.symantec.com/connect/articles/using-todays-symhelp-combat-todays-threats
Please do update this thread with more details!
With thanks and best regards,
Mick