Every time Thunderbird tries to compact the inbox the following error message is displayed. Also, Thunderbird is very slow and sluggish. "The folder 'Inbox on Local Folders' could not be compacted because writing to folder failed. Verify that you have enough disk space, and that you have write privileges to the file system, then try again." I have .97 TB of free disk space and have full control file privileges. My user account type is administrator. I have excluded the Thunderbird folder from antivirus scans and also turn off email scanning in my antivirus software. I have also started the computer in safe mode to test. None of these prevent the error message or the slowness of Thunderbird. What else can be done to prevent this error and speed up Thunderbird.