You say "POP3 in Openwebmail"... are you by any chance seeing these sent items in a POP3 client like Outlook or Thunderbird? If so they probably only exist on that client. I believe the default configuration for both for a POP3 account is to not place a copy of sent items on the server.
i try to use MSoutlook as IMAP Client.it synced all INbox but no Sent item !:).So its clear Openwebmail Pop3 service not place sent items on server.
Is there any way to get these message Back to Server ?
You would need to open whatever client you were using to connect via POP3 to the server when it was Openwebmail. Then setup this client to access Zimbra using IMAP, and then drag the messages from the Sent folder to where ever you want them on the Zimbra server.