I think there is a basic problem with the Foal database design which means that historic permalinks can be lost.
This has already been seen with the migration tool. I just realised that the same issue affects imports and archives as well. The problem is that an insert operation silently replaces any existing record. Any existing content is lost; this includes any historic permalinks. It will also affect settings such as the deleted flag. As it stands, importing a message file may cause information to be lost. With the previous release of Ponymail, I don't think this was a problem; a message archive could generally be re-imported without causing any issues.This made it very easy to backfill missing messages from archives, as there was no need to allow for existing entries. At present, I don't think it is safe to allow imports, unless they are guaranteed to be brand new. I think the mbox insert action needs to be changed to create throughout, and appropriate action taken for duplicates.
