* These are kept separate from the message itself for one of two reasons:
* 1. Either their values may change at some point after initial save, or
* 2. They are merely caches of data which exist somewhere else, for speed.
+ * DO NOT PUT BIG DATA IN HERE ... we need this struct to be tiny for lots of quick r/w
*/
struct MetaData {
long meta_msgnum; /* Message number in *local* message base */