after copying folder with 'inherit properties from parent folder' set,
the processing rules are (initially) present in the processing rules
dialogue, but are not actually written. So on a restart they are 'lost'.
This is probably the actual bug 4121, ' Moving a subfolder in another
folder erases its processing rules', rather than the description given.
*dest->prefs = tmp_prefs;
folder_item_prefs_save_config(dest);
+ prefs_matcher_write_config();
dest->collapsed = src->collapsed;
dest->thread_collapsed = src->thread_collapsed;