Re: [ietf-smtp] Draft for compressing SMTP streams

On 2016-08-18 09:29:04 +0100, Jeremy Harris wrote:
> On 18/08/16 09:07, Paul Smith wrote:
> >  (AIUI base64 encoding, even of uncompressed data, also
> > reduces compressability).
> Presumably a base64-aware compression method is not impossible?
It would be, but I would expect the difference to be slight. Assuming
that at least some of the largest mails in my office mailbox consist
mostly of an uncompressible blob (either an MS-office document
(essentially a ZIP file) or a PDF), an ideal compression would be
compress these to about 74% of their size (undoing the base64
expansion). Doing some stats on the last 30 days of mail I see some
mails which cannot be compressed to 74%, but none which are more than
76% of their original size after compression. I used gzip defaults, gzip
-9 or bzip or lzma might do slightly better. An improvement of 2%
probably doesn't warrant a non-standard compression algorithm.

        hp

-- 
   _  | Peter J. Holzer    | A coding theorist is someone who doesn't
|_|_) |                    | think Alice is crazy.
| |   | hjp(_at_)hjp(_dot_)at         | -- John Gordon
__/   | http://www.hjp.at/ |    http://downlode.org/Etext/alicebob.html

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