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 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 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 submit the same email setting Content-Transfer-Encoding: quoted-printable it passes DKIM test. So, what is the 8bit encoding here anyway and how it compared to quoted-printable? From http://tools.ietf.org/html/rfc2045#page-14, it seems that quoted-printable converts the body to something 7bit can deal with (or at least the MTA will see that header and do the convertion). What about 8bit? Is it not translated? Or, is it expected to be fed in some kind of (mime) encoded format (hence the 8bitmime) so the MTA does not touch it (hence the mime processing controls mentioned in http://www.postfix.org/cleanup.8.html)?
