Quick implementation of header compression (For OVER and XOVER functions) in python 3.3's nntplib, compression is enabled automatically after connecting to usenet, you can disable compression completely by passing a last argument (bool) when creating the NNTP or NNTP_SSL object. See the example.py for how to disable it, leaving it enabled should have no consequences however, it only affects XOVER/OVER.
If the server doesn't support compression headers will still be downloaded, uncompressed.
If the server returns an empty compressed gzip string or if there is a problem decompressing the data an NNTPDataError execption is thrown.