[Mailman-Users] collapse_alternatives

Mark Sapiro msapiro at value.net
Tue Aug 1 02:12:59 CEST 2006

Jim Popovitch wrote:

>What exactly does collapse_alternatives do?
>What is the recommended setting for collapse_alternatives?

collapse_alternatives was added in 2.1.7. The Defaults.py setting for
DEFAULT_COLLAPSE_ALTERNATIVES is Yes, which sets collapse_alternatives
to Yes for new and 'migrated' lists. I guess this makes 'Yes' the
'recommended' setting. This makes the behavior as in 2.1.6 and prior.

The 2.1.6/collapse_alternatives=Yes behavior is if filter_content is
Yes, "each multipart/alternative section will be replaced by just the
first alternative that is non-empty after filtering".

E.g. if the whole message is multipart/alternative with text/plain and
text/html subparts, even if both text/plain and text/html are accepted
MIME types, the resultant message will be 'collapsed' to just a
text/plain message containing the text/plain part and the text/html
part will be discarded.

This requires people who want to allow html on the list but filter some
other content to post html only and not multipart/alternative.

If collapse_alternatives=No, this replacement of "each
multipart/alternative section ... by just the first alternative that
is non-empty after filtering" is not done and all the alternatives
which aren't otherwise removed will remain as multipart/alternative
subparts in the final message.

Note that if you set collapse_alternatives=No, you almost certainly
also want to set convert_html_to_plaintext=No.

Mark Sapiro <msapiro at value.net>       The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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