When I try and "Compact" my trash folder, I get the following error message: "The folder 'Trash on paul.landsbergis@gmail.com' 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."

There is plenty of disk space, but there is no option for "write privileges". The trash folder has grown to 632 MgB even though I keep deleting old messages from the trash folder!