Once upon a time, it made sense to do automatic character set encoding
conversions on the fly. With the advent of pretty much obligatory
message DKIM signing, this option has become a bit of a liability, being
able to check email message signature validity even after they are
written in your mailbox is useful.

Unfortunately on an older system I help to administer, sendmail 8.14.4
does automatic conversions from quoted-printable to 8bit when messages
are pushed to the local mailer, and I haven't been able to figure out
how to completely disable these conversions.

Messages without quoted-printable get sent correctly through, and the
DKIM signature is correct in mailbox. Messages with quoted-printable
(which were verified to have valid DKIM signing by an intermediate mail
forwarder that added ARC headers) get converted and tagged with:

X-MIME-Autoconverted: from quoted-printable to 8bit by HOST id MESSAGE

Looking at http://www.sendmail.org/~ca/email/doc8.12/op-sh-5.html#sh-5.4
I assumed that replacing the "9" with "8" in the Mlocal flags would
rectify this. I did this by adding into sendmail.mc the lines

MODIFY_MAILER_FLAGS(`LOCAL', `-9')dnl
MODIFY_MAILER_FLAGS(`LOCAL', `+8')dnl

and these caused sendmail.cf Mlocal flags to change:

> Mlocal, P=/usr/bin/procmail, F=lsDFMAw5:/|@qSPfhn9, S=EnvFromL/HdrFromL, R=EnvToL/HdrToL,
---
< Mlocal, P=/usr/bin/procmail, F=lsDFMAw5:/|@qSPfhn8, S=EnvFromL/HdrFromL, R=EnvToL/HdrToL,

But unfortunately this didn't seem to make a difference. Is this
something hardwired into this older sendmail, or have I just
misunderstood which part of the mailer does the conversion?

Otto J. Makela wrote:

> Unfortunately on an older system I help to administer, sendmail 8.14.4
> does automatic conversions from quoted-printable to 8bit when messages
> are pushed to the local mailer, and I haven't been able to figure out
> how to completely disable these conversions.

Recompile the code without setting these options:
MIME8TO7 If non-zero, include 8 to 7 bit MIME conversions. This
also controls advertisement of 8BITMIME in the ESMTP
startup dialogue.
MIME7TO8 If non-zero, include 7 to 8 bit MIME conversions.

> X-MIME-Autoconverted: from quoted-printable to 8bit by HOST id MESSAGE

> Looking at http://www.sendmail.org/~ca/email/doc8.12/op-sh-5.html#sh-5.4

That's really old...

> I assumed that replacing the "9" with "8" in the Mlocal flags would
> rectify this. I did this by adding into sendmail.mc the lines

8 If set, it is acceptable to send eight bit data to
this mailer; the usual attempt to do 8->7 bit MIME
conversions will be bypassed.

Looks like a good idea, but are you sure the conversion happens
when that mailer is used (maybe it happened before)? Is that mailer
even used? Check the log entry.

What is your setting for:
EightBitMode=action
[8] Set handling of eight-bit data. There
are two kinds of eight-bit data: that de-
clared as such using the BODY=8BITMIME ESMTP
declaration or the -B8BITMIME command line
flag, and undeclared 8-bit data, that is,
input that just happens to be eight bits.
There are three basic operations that can
happen: undeclared 8-bit data can be auto-
matically converted to 8BITMIME, undeclared
8-bit data can be passed as-is without con-
version to MIME (``just send 8''), and de-
clared 8-bit data can be converted to 7-bits
for transmission to a non-8BITMIME mailer.
The possible actions are:

s Reject undeclared 8-bit data (``strict'')
m Convert undeclared 8-bit data to MIME (``mime'')
p Pass undeclared 8-bit data (``pass'')

In all cases properly declared 8BITMIME data
will be converted to 7BIT as needed. Note:
if an automatic conversion is performed, a
header with the following format will be
added:

X-MIME-Autoconverted: from OLD to NEW by $j id $i

where OLD and NEW describe the original for-
mat and the converted format, respectively.

--
Note: please read the netiquette before posting. I will almost never
reply to top-postings which include a full copy of the previous
article(s) at the end because it's annoying, shows that the poster
is too lazy to trim his article, and it's wasting the time of all readers.