Sven Radej wrote:
> 
> Please advice:

If you haven't already done so, look at rfc822.
(http://ftp.snt.utwente.nl/misc/rfc/rfc822.txt)

> KMail when replying sets header "References" in which it puts msg-id of the
> original message (i.e. of message to which we reply now).
> 
> Pine sets the same thing in "In-Reply-To"
> 
> Question:
> 1.) Should I add the header "In-Reply-To" with original message ID (clone
> "References") as Pine does? Gnus v5.5 does it this way:
> [In-Reply-To: Sven Radej's message of "Wed, 9 Jun 1999 15:15:46 +0200"]
> Is this wrong? Is it important after all?
> 
> 2) I saw that some mails have more references in "References" header. Where to
> they come from? I mean you can reply to only one mail at a time.

RFC822 says:
>      optional-field =
>                  /  "Message-ID"        ":"   msg-id
>                  /  "Resent-Message-ID" ":"   msg-id
>                  /  "In-Reply-To"       ":"  *(phrase / msg-id)
>                  /  "References"        ":"  *(phrase / msg-id)
>                  /  "Keywords"          ":"  #phrase
>                  /  "Subject"           ":"  *text
>                  /  "Comments"          ":"  *text
>                  /  "Encrypted"         ":" 1#2word
>                  /  extension-field              ; To be defined
>                  /  user-defined-field           ; May be pre-empted

So In-Reply-To / References may either contain a 'phrase' like Gnus uses
or a msg-id (like Pine does). A msg-id looks much more usefull to me,
since this can be used to automatically retrieve the original message.

RFC822 also says
 
> 4.6.2.  IN-REPLY-TO
> 
>              The contents of this field identify  previous  correspon-
>         dence  which this message answers.  Note that if message iden-
>         tifiers are used in this  field,  they  must  use  the  msg-id
>         specification format.
> 
> 4.6.3.  REFERENCES
> 
>              The contents of this field identify other  correspondence
>         which  this message references.  Note that if message identif-
>         iers are used, they must use the msg-id specification format.

My interpretation would be that you put a single msg-id of the message you
respond to in the IN-REPLY-TO header and that you add the IN-REPLY-TO 
header of the msg you reply to to the REFERENCES header of the msg you
reply to and put these in the REFERENCES header.

Example:

Msg 1
-----
Message-ID: Msg1

Msg 2
-----
Message-ID: Msg2
In-Reply-To: Msg1

Msg 3
-----
Message-ID: Msg3
In-Reply-To: Msg2
References: Msg1

Msg 4
-----
Message-ID: Msg4
In-Reply-To: Msg3
References: Msg1, Msg2

This makes it easy to keep related messages together. (E.g. build a thread).

It does look though as if some mailers don't use In-Reply-To and add the msg-id
directly to the References header. This isn't very well defined I'm afraid.


> 3) I have reason to belive that "X-Loop" should in no circumstances end in To:,
> Cc: or Bcc: field. Am I right?

"X-" suggests this is a user-defined header. I assume this is used by mailing-
lists/MTA's to detect mail-loops. Ignore it/don't use it.

RFC822 says:
>      4.7.5.  USER-DEFINED-FIELD
> 
>              Individual users of network mail are free to  define  and
>         use  additional  header  fields.   Such fields must have names
>         which are not already used in the current specification or  in
>         any definitions of extension-fields, and the overall syntax of
>         these user-defined-fields must conform to this specification's
>         rules   for   delimiting  and  folding  fields.   Due  to  the
>         extension-field  publishing  process,  the  name  of  a  user-
>         defined-field may be pre-empted
> 
>         Note:  The prefatory string "X-" will never  be  used  in  the
>                names  of Extension-fields.  This provides user-defined
>                fields with a protected set of names.


> I am looking for sponzor to reward people who answer correctly to my questions
> ;-)

I bet I win a free copy of a certain mail program :)

Cheers
Waldo
-- 
KDE, A New Millenium, A New Desktop                      http://www.kde.org