Re: Why does Gnus generates Lines: header in mail?

[Stainless Steel Rat <ratinox@peorth.gweep.net>]

* Simon Josefsson <jas@extundo.com>  on Sun, 29 Sep 2002
| X-* is blessed by the standard to contain experimental stuff, so I don't
| see a problem there.  Mail-Copies-To has value and even interoperates
| fairly well.  If Lines: has value, I won't continue argue it should be
| removed, but I haven't understood where that value is.

The purpose of Lines is quite simple: it gives a ballpark estimate as to
the size of a message, thus allowing the client the ability not to download
messages that exceed a particular size.

For example, POP does not have a mechanism by which it can determine the
size of messages.  But it can get all the headers.  A POP client can grab
the headers of all messages, check the Lines headers for each, and skip any
messages that exceed a user-defined threshold.  This is useful, for
example, if you happen to be a travelling sales engineer currently
somewhere in India using a cellular/gsm phone at 9600 baud to download your
mail but don't want the 150MB PowerPoint presentations that your manager
sent out to everyone, at least not until you get back to your office and a
T1.  I am not making this up.  I have an SE who routinely does this.

On the Usenet side of things, Gnus Agent uses Lines headers the same way,
to determine if a message qualifies as "long" and does not automatically
retrieve articles that exceed the "long" threshold.

-- 
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