From: Alex van den Bogaerdt (alexergens.op.het.net)
Date: Tue Jun 01 2004 - 19:32:02 CDT

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On Wed, Jun 02, 2004 at 02:04:58AM +0200, Cami wrote:

> A large amount of my userbase is very confused by the From:/To: fields
> that Postfix inserts.. (especially when they try to reply to the mail..)

Thank you. You understand the problem.

Do you have numbers on how many of such mail is malformed but otherwise
valid email? And how many of those do have a message-id?

As far as I can tell:
- mail without a message-id is spam or virus, perhaps a few exceptions
- those messages often have spoofed or non-fqdn headers
- the subject of filtering on a missing message-id has come up before
   (as has the subject of non-FQDN from: and to:)
- adding a message-id is only optional as far as rfc822 is concerned
- adding a message-id is only optional as far as rfc2821 is concerned,
  and several warnings are included such as this one:
  "This strategy is generally considered appropriate when the server can
   identify or authenticate the client, and there are prior agreements
   between them. By contrast, there is at best great concern about fixes
   applied by a relay or delivery SMTP server that has little or no
   knowledge of the user or client machine."
- adding a message-id is specifically forbidden by rfc2821 when an MTA
  is an intermediate (such as: spammer->MTA1->MTA2->destination when
  postfix is MTA2)
- Correcting addresses to proper FQDN format is specifically forbidden
  by rfc2821 when an MTA is an intermediate
- currently there's no way (AFAIK) to make postfix NOT add/correct the
  headers despite the MUST NOT as discussed

So therefore I stand by my claim that adding a message-id is wrong. In
the message itself I stated that opinions and setups may differ so the
process should be configurable. I regret if my wordings are misinterpreted
however I have done my homework.

cheers,
Alex
--
I ask you to respect any "Reply-To" and "Mail-Follow-Up" headers. If
you reply to me off-list, you'd better tell me you're doing so. If
you don't, and if I reply to the list, that's your problem, not mine.

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