Are you looking for the method to export ost files to zimbra then you should try
WebbyAcad OST Converter.
- Download the Software > Open the OST File > Preview the Mail File.
- Select the File Format Zimbra > Add the Zimbra Login details > Choose the Folder > Press Export Button
After the Conversion completed re-check the Mailbox files once for ensure of data security.
Also Read :- Top method to Export OST File to Zimbra 
