From Zimbra :: Wiki
To receive e-mail updates on the progress of the bug fix, enter your e-mail address in the "Add CC" box located at the top right of the bug page and click the "Commit" button located on the left side down the page before the comments. You will receive an e-mail every time someone leaves a comment or otherwise changes the bug. You can fine tune this behavior in your bugzilla e-mail preferences.
If you would like to report a bug, please first search the database to determine if the bug has already been reported. If it has, feel free to add your comments to the bug; if not, then enter a new bug report.