Update: this is working almost too well! As I watch Get Mail get, say 14 messages, only 10 appear in my inbox. The others are identified and ZAPPED instantaneously. They don't appear in the Trash folder either! (I double-checked by logging into my ISP's webmail server where copies of all messages are saved until I manually delete them, and there they were, the irritating bouncebacks.)
There may be a down-side to this efficient filter.....
