1xx - Informative message 2xx - Command ok 3xx - Command ok so far, send the rest of it. 4xx - Command was correct, but couldn't be performed for some reason. 5xx - Command unimplemented, or incorrect, or a serious program error occurred.
x0x - Connection, setup, and miscellaneous messages x1x - Newsgroup selection x2x - Article selection x3x - Distribution functions x4x - Posting x8x - Nonstandard (private implementation) extensions x9x - Debugging output