It appears to me that filter rules of the type "move to folder" use some "number" to identify the destination folder, and that these identifiers are liable to change. Symptom: several times some action (migrating data to a different computer, upgrading, restoring data from backup) results in all "move to folder" rules either having the wrong target folder or no target folder. Proposed solution: store the folder path instead of what I assume is some numeric ID in the rule configuration. (Is my assumption that a simple numeric enumeration is used correct? It does not seem a robust solution.) Reproducible: Sometimes
No we can't do it. But you can export filter which export with path and reimport it in new computer, filter manager will try to find correct folder and adapt it. Regards.
It's not moving to a new computer that's the problem, it's update problems or file corruption or one of any number of causes (I'm not sure exactly what, but as I said it's happened to me several times). Don't you agree that robustness is a very important thing in a mail client?