Mauricio Tavares:
> This email is mostly about understanding what is going on, how
> the process works than whether my install of postfix is working
> properly or the MUA is lying. In fact, I am using ssmtp to send the
> email to postfix because I want to make my test as simple as possible
> (avoid "helpful" MUAs adding stuff to the email). So, let's say I
> create simple email:
>
> raub@desktop:~$ cat 8bit_test
> Subject: 8bit test
> Content-Transfer-Encoding: 8bit
>
> Text with umlauts here
This email requires a MIME-Version header. Otherwise it is
not valid MIME.
> raub@desktop:~$
>
> It only has two headers (the From: header is added when I actually
> send email) and a single line in the body, which has a few 8bit
> characters. I am using ssmtp to send the above email to my postfix
> server,
>
> ssmtp -v r...@domain.com < 8bit_test
>
> which is setup to do DKIM and announces that supports the following
>
> 250-PIPELINING
> 250-SIZE
> 250-ETRN
> 250-STARTTLS
> 250-ENHANCEDSTATUSCODES
> 250-8BITMIME
> 250 DSN
If the client sends 8BITMIME, then it MUST issue the 8BITMIME keyword
on the MAIL FROM command line. Otherwise, behavior is undefined
(i.e. different systems may handle this in different ways).
> What I have noticed is that it will fail DKIM, and then will change
> the Content-Transfer-Encoding: header to quoted-printable. Now, if I
As required by the MIME RFCs, an MTA must either bounce mail or
convert it to quoted-printable when it needs to deliver 8BITMIME
mail to an SMTP server that does not announce 8BITMIME support.
DKIM signatures of 8BITMIME mail may break unless all SMTP servers
in the path implement and announce 8BITMIME support. Otherwise, it
is better to down-convert to quoted-printable before DKIM signing.
Wietse
