how to free up space from deleted open file? [duplicate]
You have a running process writing to the file. You should have truncated or zeroed the logfile instead of deleting it. See the detail and explanation of the process here, but something like : > /path/to/sync.log would work.
At this point, you'll have to restart the Zimbra daemon to realize the newly-freed space.
Obviously, this is treating the symptom, and you'll hopefully have an opportunity to fix this at the Zimbra level.
The better way to delete a file that is being written to is simply cp /dev/null into it
cp /dev/null /path/to/file