Upon updating to version 10.4, the “Move to Folder” setting in all of my mail rules lost/reset the defined folder.
Workaround/fix: manually edit each rule to reset the “Move to Folder” setting by re-selecting the correct folder for each.
This appears to be a bug related to the update to Version 10.4. Posting it here, in case it is helpful for anyone else who might have observed rules no longer working properly.
(If there is somewhere else/a better way to report a bug, I’d be happy to do it.)