I think bdial missed or misunderstood the use of lmtpinject. It is true that finding and restoring the files in /opt/zimbra/store is not sufficient. They need to be imported via rest or lmtp. lmtpinject does literally the same thing as a new incoming email (post-antivirus and antispam checks).
If the user cares about the "Received" date being correct, you might have to get a little fancy with an x-zimbra-received header. |