It typically could be any one of several conditions:
 
1) the user has sent it twice
 
2) the mail transport system(s) have tried to transport it twice,
   due to mail spools being reloaded or failed acknowledgements
   of the SMTP processes
 
3) maybe a mail loop of some sort.
 
Usually a careful comparison of two of these messages' RECEIVED
headers will reveal which host/process is engaging in the
duplicative behaviour.
 
--  co-owner INFOSYS, TQM-L, CPARK-L, ERAPPA-L, JANITORS, LDBASE-L, et -L
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