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From: barmar@think.com (Barry Margolin)
Newsgroups: comp.mail.misc
Subject: Re: Procedure for adding headers?
Message-ID: <1990Nov21.170229.16590@Think.COM>
Date: 21 Nov 90 17:02:29 GMT
References: <3235@exodus.Eng.Sun.COM> <1990Nov21.084347.25984@Think.COM> <1990Nov21.095143.16696@morrow.stanford.edu>
Sender: news@Think.COM
Organization: Thinking Machines Corporation, Cambridge MA, USA
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In article <1990Nov21.095143.16696@morrow.stanford.edu> mpyoung@elaine49.stanford.edu (M. Pinghua Young) writes:
>In article <1990Nov21.084347.25984@Think.COM> barmar@think.com (Barry Margolin) writes:
>>I can't find the Precedence field in RFC822.
>Look it up in UNIX installation guide for sendmail.

The installation guide for sendmail is not a standards document.  As you
pointed out, sendmail includes quite a few extensions to RFC 822.

>A side note:  you can also specify a header of "Returned-Receipt-To: ", in
>which case the receiving sendmail will generate a receipt automatically to
>the e-mail address specified in that field.

Multics provides something like this, but it has a different field name
(Acknowledge-To).  However, the receipt is generated by the user agent, so
that you know when the user actually read the mail; it also sends a
different receipt if the user deletes the message without ever reading it.
Users who prefer privacy can tell their UA not to generate
acknowledgements.

>Another header which is mostly used in mailing list is called "Errors-To:".
>If this is present, any error messages will be delivered to the specified
>address in addition to the sender.  Useful (obviously) for maintaining a
>mailing list.

That's what the SMTP "MAIL FROM" command is supposed to be for; X.400 has a
similar envelope field.  Errors-To may be necessary for some non-SMTP MTAs
that store control information in the header, though.  Ideally, though, all
mail transfer protocols would pass MTA control information separately from
the message data.  This layered approach would allow the MTA protocols and
the message format standards to evolve independently (e.g. if one wanted to
use SMTP to transfer X.400-format messages).
--
Barry Margolin, Thinking Machines Corp.

barmar@think.com
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