From: Alex van den Bogaerdt (no email)
Date: Tue Jun 01 2004 - 12:05:37 EDT
On Wed, May 26, 2004 at 10:55:01AM +0200, Andrzej Kukula wrote:
> A question: what particular problem that might concern majority of Postfix
> users is OP trying to solve???
Changing the message header for mail in-transit, or rather avoiding it.
RFC2821 applies (and postfix claims conformance IMHO):
There's a strong ` MUST NOT ' in the next snippet. There's also a warning
about having to be cautious because it's easy to get it wrong. And indeed
postfix gets it wrong IMHO.
" The following changes to a message being processed MAY be applied
when necessary by an originating SMTP server, or one used as the
target of SMTP as an initial posting protocol:
- Addition of a message-id field when none appears
- Addition of a date, time or time zone when none appears
- Correction of addresses to proper FQDN format
The less information the server has about the client, the less likely
these changes are to be correct and the more caution and conservatism
should be applied when considering whether or not to perform fixes
and how. These changes MUST NOT be applied by an SMTP server that
provides an intermediate relay function.
"
Note that "the following changes" are allowed at the origin, not on an
intermediate relay!
A spammer sends mail with just a bare "From: spammer" as the RFC822
sender address. Postfix appends $myorigin to it. Users get mail
from a supposedly local user. Difficult to explain to them *that*
postfix adds its own name, not possible to respond to the general
response of "But... thats stupid. Why does it do that?"
Message-Id is similar, now $myhostname is appended.
Workarounds have proven to be problematic. An extra instance, or
some /etc/postfix/master.cf changes, make it possible to change
the appended text. Extreme caution is needed for bounces, double
bounces and aliases (especially aliases).
> Maybe instead he would invent something to stop 100% of spam ;)
That is already invented, it is called a wire cutter. Apply to
the receiving mail gateway; then apply to any local spammer if at
all present. Bit drastic :)
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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