I have Zimbra Desktop setup using IMAP. I have the box ticked to save sent mail in Sent folder from the Composing tab. It is not saving it anywhere. I checked my Webmail Sent folder with the provider and it is not there either. If I send with Thunderbird, it does show up in the Sent folder and syncs with Zimbra. I also have a POP account set up and have the same problem.