Ralf Hildebrandt via Postfix-users:
> * Wietse Venema via Postfix-users <[email protected]>:
>
> > > Well, who knew stuff like this would happen. I wasn't aware, and
> > > obviously there's quite a lot of broken systems out there...
> >
> > I'm surprised. You mentioned seeing a dozen, out of how many messages
> > was that, and what was their origin like (commercial transaction,
> > discussion forum, business correspondence)?
>
> In the last 7 Days I'm seeing 7 mails in total (which is only a
> minuscule fraction of our mail):
>
> Two from a bank (kotak.bank.in) and five from cpms2.ern-net.eu, so
> both are of official nature.
>
> kotak.bank.in seems to use something with Java:
> Message-ID: <xxxx.yyyy.JavaMail.wasadmin@KBPRVMUW00236>
>
> cpms2.ern-net.eu has nothing obvious in the headers.
I expect that inserting the missing empty line will not break DKIM
signatures, because that empty line is officially not part of the
header or body. According to RFC 5322 section 2.1:
the body [...] is separated from the header section by an empty line
For Sendmail compatibility, the Postfix Milter client does not send
the first body line to a Milter (for example, to a DKIM signer or
verifier). In the case of Postfix, that first line is always empty,
because Postfix inserts an empty line if one is not already present.
I expect that other DKIM signers and verifiers will also skip the
empty line that separates the header from the body; if they did not
skip it, then DKIM would never have worked.
> > I would expect that application developers use existing libraries
> > to generate email messages, and that broken headers are more likely
> > with illegitimate email generators (i.e. email that no-one cares
> > about).
>
> So would I :)
The same software that will send lines with lengths that exceed the
SMTP spec ;-(
Wietse
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