After migrating to zimbra, all the users have messages in their Sent folder which do not have the "sent by me" message flag set. I was in the middle of writing a script to solve this problem when I realized the zmmailbox command's "flag" functions relate to importance flags, not zimbra's message flags. How can I mark existing messages with the "sent by me" flag using CLI tools, or how can I do it in bulk (or at all) from the web interface (or any)?

Message Flags - Zimbra :: Wiki