On February 13 2005 Reiner Steib wrote in gnu.emacs.gnus:

> On Sat, Feb 12 2005, Pedro Kroger wrote:
> > I started tracking the problem down and it seems that the culprit is
> > multipart email sent by Microsoft Outlook Express 6.00 (or something
> > like that). It seems that gnus can't see others emails beyond that
> > point.
> 
> > Here is an example. This mbox file:
> 
> > http://www.pedrokroeger.net/gnus/bug-gnus
> 
> > has 2 messagens, as can be seen here in mutt:
> 
> > http://www.pedrokroeger.net/gnus/mutt-summary.png
> 
> [ I didn't look at this because I'm offline. ]
> 
> > But if I try to see this file in gnus using nndoc, I can see only one
> > message and it's parts: [...]
> 
> Concerning nndoc: Did you try the prefix argument of
> `gnus-group-make-doc-group' (C-u G f)?
> 
> ,----[ (info "(gnus)Foreign Groups") ]
> | `G f'
> |      Make a group based on some file or other
> |      (`gnus-group-make-doc-group').  If you give a prefix to this
> |      command, you will be prompted for a file name and a file type.
> |      Currently supported types are `mbox', `babyl', `digest', `news',
> |      `rnews', `mmdf', `forward', `rfc934', `rfc822-forward',
> |      `mime-parts', `standard-digest', `slack-digest', `clari-briefs',
> |      `nsmail', `outlook', `oe-dbx', and `mailman'.  If you run this
> |      command without a prefix, Gnus will guess at the file type.  *Note
> |      Document Groups::.
> `---- 

The issue has to do with nndoc groups built on mboxes.

Yes, the C-u prefix with the correct type seems to work.  But, absent
the prefix, interpreting a correct mbox with hundreds of messages as
only the list of mime-parts of a single message makes gnus looks very
silly.

I've seen this latency occasionally over the years, and I now believe
there is a bug though I have not looked into the code.

The problem happens when the first message in an mbox is multipart.
(It has nothing to do with Outlook; an example may be created entirely
using gnus.)

Here's what I did.

I made a simple HTML file and then used "lynx" to dump it to text.
I then mailed two messages to myself, the first a simple text message
consisting of the dumped text and the second a multipart message composed
in gnus with two attachments (disposition = attachment) where the first is
the dumped text and the second is the html version.

I then retrieved the two messages using gnus (nnmbox backend) and
saved both messages in two different mboxes that differ only in the
question of which of the two messages is saved first.

A new nndoc group built on the mbox that begins with the simple
message is handled correctly when read in gnus, but a new nndoc group
built on the other mbox (without prefix argument) is interpreted
incorrectly.

The most recent set-up I know where this experiment goes as I described
is emacs 22.1.1 with gnus v5.11, as packaged natively for Ubuntu 8.04.

                                    -- Bill