Bill, As you suggested I did use zmlmtpinject. I'm not very sure if results were optimum but It worked. Once I knew where to find the user's mailbox I run this command
/opt/zimbra/bin/zmlmtpinject -s dpiccolo /home/administrador/zimbra/20101031/store/0/59/msg/0/* -r
dpiccolo@unitan.net
It copied more than 600 messages to the inbox. Then I searched for the ones sent by Piccolo and moved them to the Sent folder. Mails lost their original date and time but it could be worst.
Do you think I can improve the restore process?
Thanks once again,
Pancho