Great Circle Associates Majordomo-Workers
(January 1999)

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Subject: Re: A question re. Majordomo and RFC 822 required headers
From: Norbert Bollow <nb @ thinkcoach . com>
Date: Wed, 6 Jan 1999 23:36:19 +0100
To: majordomo-workers @ GreatCircle . COM
Cc: george @ oldzoom . bga . com, mouse @ fmp . com, tibbs @ hpc . uh . edu
In-reply-to: <> (message from Jason LTibbitts III on 04 Jan 1999 23:59:20 -0600)
Prefer-language: de, en, fr
References: <> <>

Lindsay Haisley <> wrote:

> I recently encountered a situation in which certain messages resent by
> Majordomo to list zubscribers at an ISP were being bounced by the ISP's
> spam filters with the message "550 Body To: is missing or empty".

Jason Tibbitts <> replied:

> The ISP that's bouncing the message is violating a very important
> principle, the Robustness Principle: be conservative in what you generate
> and liberal in what you accept (RFC1123 1.2.2).  If Majordomo were to
> reject the message, it would be violating that principle.

Hmm... is it possible to do spam filtering without violating the
robustness principle?

> Correct.  I try to follow the principle of "least header modification",
> meaning that the headers should be left as close as they were originally
> because the mailing list manager only forwards the message.  The actual
> requirements are (again) rather vague; my view is that Majordomo shouldn't
> make things look any different than a simple Sendmail alias list.

Yes. This "principle of minimal munging" is strongly supported by the
following section in RFC1123:

      5.3.6  Mailing Lists and Aliases

         An SMTP-capable host SHOULD support both the alias and the list
         form of address expansion for multiple delivery.  When a
         message is delivered or forwarded to each address of an
         expanded list form, the return address in the envelope
         ("MAIL FROM:") MUST be changed to be the address of a person
         who administers the list, but the message header MUST be left
         unchanged; in particular, the "From" field of the message is

> LH> Would it be appropriate to add code to Majordomo to either a) reject
> LH> posts not containing a To: header
> That is your choice; in Majordomo2 (this is the workers list, after all),
> add an entry like
> !/^To:/i
> to taboo_headers.  Majordomo1 cannot do this without code modification, but
> such a hack would be relatively simple.
> LH> or b) to insert a To: header with the list address into posts in which
> LH> a To: header is absent?
> I don't believe that's really acceptable.

I agree with Jason's comments. As list-owner, you can decide that
the lack of a proper To: header makes a message unacceptable for your
list, but I feel that allowing mailing list software to attempt to
"repair" To: headers is a really very bad idea. Debugging mail loops and
the like can be hard enough already without another source of confusion.

> Slightly more acceptable would
> be to add something like
> To: No-To-Header-Present;:

When you send a message with a To: header like this to a big mailing
list you're going to get quite a few bounces from MTAs and spam filters
who don't like this kind of To: header. It simply doesn't help.

May blessings from the eternal God surprise and overtake you!

Norbert Bollow, Zuerich, Switzerland. Backup e-mail address: NB@POBOX.COM

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