When receiving email, I often get the following Alert message for items I have setup for filtering: The messages could not be filtered to folder 'folder-name' 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. Neither of the possible issues stated are true. I have several filters. Some work fine while others fail. If I subsequently Run Filters on Folder option against the Inbox, all filters run without issue. I have tried compacting the folders as well as rebuilding the global database indexes, but the problem persists.