We are using opensource edition of Zimbra 6 in 64bit RHEL 5 machine.
We have using opensource version backup restore mentioned in this wiki.
Backing up and restoring Zimbra (Open Source Version) - Zimbra :: Wiki
We took more than 400 users mail backup using the above script successfully.
While restoring we faced the following error for few users. Kindly guide us to solve this issue.
Restoring files from backup firstname.lastname@example.org ...
 INFO: I/O exception (java.net.SocketException) caught when processing request: Broken pipe
 INFO: Retrying request
ERROR: zclient.IO_ERROR (Unbuffered entity enclosing request can not be repeated.) (cause: org.apache.commons.httpclient.ProtocolException Unbuffered entity enclosing request can not be repeated.)