[Email-SIG] Generating zipped or gzipped attachment with emailpackage?

[Stephen J. Turnbull]

Mark Sapiro writes:

 > Ideally, one would be able to specify a parameter on the Content-Type;
 > header along the lines of
 > 
 > Content-Type: text/csv; charset="utf-8"; compression="gzip"

No, I think this is really a content transfer encoding, not part of
Content-Type, and I don't see why one would be enough.  Nor would it
necessarily always be compression.

So how about a Content-Transfer-Filter header which resolves to an
(order-sensitive!) list of transformations:

Content-Transfer-Filter: pgp-encrypted; algorithm=idea; order=3
Content-Transfer-Filter: x-xz; order=2; comment="the successor to LZMA";
  alternate-application=x-lzma
Content-Transfer-Filter: base64; order=1

Order is "decoding order" here.  Otherwise you'd need a parameter to
determine which to use first (in case of corruption or reordering by
some brain-damaged MUA or MTA).

In the presence of a Content-Transfer-Encoding header, the
Content-Transfer-Encoding should be applied first, then any
Content-Transfer-Filters.