[R] How to reply to a thread if receiving R-help mails in di

(Ted Harding) Ted.Harding at nessie.mcc.ac.uk
Sun Aug 13 16:21:15 CEST 2006

On 13-Aug-06 Dirk Enzmann wrote:
> I receive R-help messages in digest form that makes it
> difficult to answer a post. I noticed that my answer is
> not added to the thread (instead, a new thread is started)
> although I use the same subject line (starting with "Re: ")
> as the original post. Is there a solution (I prefer the
> digest to separate messages for several reasons and don't 
> want to change my email reader)?
> The way I answer post up to now is:
> 1) I press the reply button of my email program (Mozilla /
> Thunderbird, Windows)
> 2) I delete all contents of the digest except for the post
> (including name and mail address of the posting person)
> I want to answer so that the original question will be
> included (cited) in my answer.
> 3) I add the email address to the individual sender to "cc:"
> to the automatically generated address of the R-help list.
> 4) I replace the automatically generated subject line (for
> example "Re: R-help Digest, Vol 42, Issue 13" by "Re: "
> followed by a copy of the original subject line of the post.
> 5) I write my answer and send the mail to the mailing list.
> It's not that this is tedious - the problem is that the
> thread is broken. Is there a better way even if I want to
> keep receiving messages in digest form? The posting guide
> is silent about this.
> Dirk

It may be that you are stuck with the "new thread" phenomenon,
though others more knowledgeable that I am may have other ideas.

It depends (at least in part) on headers associated with each
individual message in the digest, as well as the subject itself.
Again, since I don't receive R-help in digest form, I can't tell
whether these are helpful.

If you are receiving email "normally" from a list, you will
find headers like "In-Reply-To:" and "References:" in a message
which continues a thread, as well as a "Message-ID:" for the
message itself. An example from another list:

In-Reply-To: <20060811180225.GA16232 at mx0.halon.org.uk>
Message-ID: <Pine.LNX.4.64.0608121102380.27772 at seagull>
References: <20060811180225.GA16232 at mx0.halon.org.uk>

This enables mailing-list software to keep track of the messages
in a thread, since the "previous" message is identified in the
"In-Reply-To:" and "References:" headers by its own "Message-ID:",
and the "Message-ID:" for the current message can be picked up
and used in a similar way in further follow-ups.

Now I am currently receiving allstat in digest form. When I look
at the headers for each message in the digest I see the likes of
(which *is* a reply to a preceding message and therefore the
second message in a thread):

Date:    Sun, 6 Aug 2006 11:34:41 -0700
From:    Steve <steve_beaney at YAHOO.COM>
Subject: Re: Unsubscribe!
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit

and so there is nothing in these headers to identify the message
that it is a reply to (the subject line not being a unique
identifier, of course).

The "Subject:" itself doesn't really count. Indeed, often people
start a new topic on a list by "replying" to a message, simply
to lazily avoid entering the list address. So they press the reply
button and preserve the list address, then delete everything else
and start "afresh" with a new subject line and whatever they want
to say, which has nothing to do with the thread they are "replying"

But, as people who've experienced this will know, the effect is
that it will be handled as if it were a continuation of the thread,
albeit with a new subject. When others on turn reply to that message,
these replies (on a different topic) will get wrapped into the old
thread. This is called "hijacking the thread". When you visit the
list archives, you will find threads with a block of messages
in the middle which have "changed the subject". And all because
of the above headers.

So, unless the R digestifier is obliging enough to insert thread
referencing headers for each message in the digest ("Message-ID:"
headers at least), unlike allstat, I don't think you can avoid
starting a new thread with your reply.


That being said, if you receive a lot of list digests it may still
be worth considering a change of email client (assuming that Mozilla
or Firefox cannot be configured to handle digests appropriately).

>From your description of how you reply, it seems that you see
every message at once in the "display message" window.

A digest is a type of MIME structure, denoted as

  Content-Type: multipart/digest; boundary="..."

and in effect each part is like an "attachment". If your email
client recognises this structure, you should see a list of the
separate parts of which the first will describe the subjects
in the remaining parts. For example, the digest I took the above
examples from has 3 parts which show as:

1 message/rfc822    8-bit    us-ascii
2 message/rfc822    8-bit    us-ascii
3 message/rfc822    8-bit    us-ascii

and if I open the first one I see

  There are 2 messages totalling 77 lines in this issue.

  Topics of the day:

    1. Unsubscribe! (2)

which tells me that there are two messages, each with the
same topic "Unsubscribe!".

Number 2 is the original "Unsubscribe!" message, and number 3
is the reply to it (cited above).

In my XFMail client (not available as far as I know for Windows),
if I double/middle click on any one of these three I read that
message directly. It also has a "Next" and "Previous" button on
any open message, so I can scroll sequentially through them,
seeing only one message at a time (and not getting them all
at once). I can reply-to/forward etc. any single message.

This has to be more convenient for reading and dealing with
digest format than the all-at-once you are experiencing in

Hoping this is useful,

E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 13-Aug-06                                       Time: 15:21:09
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