Forum Discussion
Microsoft's e-mailservers break DKIM on non-ascii characters
There seems to be some kind of character encoding issue in DKIM signatures applied by Office365 servers. We just had a DKIM fail ('body hash did not verify') and tracked it down to non-ascii quotes b...
I dove into it a bit more. The mail client is supposed to deliver the content using quoted printable encoding, so only 7 bit ascii (alphanumerics and =). This is the 'Content-Transfer-Encoding', different from the CONTENT encoding, which can still be UTF-8 (in which case µ will be =C2=B5).
I tried specifying 8 bit as content transfer encoding, but that didn't help.
However, ultimately, the mail client is the original offender, because that apparently just dumps UTF8 bytes into SMTP.
I tried specifying 8 bit as content transfer encoding, but that didn't help.
However, ultimately, the mail client is the original offender, because that apparently just dumps UTF8 bytes into SMTP.
Actually, this is still not it. I tested clients that do proper quoted printable, and it fails. And Postfix +OpenDKIM does handle the above shellscript properly.