[Exim] RE: mmdf and things

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Autor: Jim Segrave
Datum:  
To: exim-users
Betreff: [Exim] RE: mmdf and things
> Subject: Re: [Exim] Forgive my ignorance ...
> From: Tony Earnshaw <tonni@???>
> To: exim-users@???
> Cc: dsh8290@???
> Date: 28 Mar 2002 19:23:39 +0100
>
> --
> tor, 2002-03-28 kl. 06:55 skrev dman:
>
> > Mmm, read the docs. exim only sends out 8-bit data if it was stuck in
> > it. The docs on the advertise_8bitmime option also clearly say that
> > it is not standards conforming and is likely to cause problems.
>
> He says, and has never said, anything of the sort.
>
> Don't forget that I've been with Exim since more or less the start, and
> that my memory is that of an eliphant.
>
> What Phil says/said, that many MTAs can get broken by it.


And he is correct.

> In the mean time, Sendmail with 8-7 bit translaton has appeared, and
> most other MTAs apart from Erfc1652xchange are disappearing. Read, mark,
> learn and inwardly digest rfc1652.
>
> > Funny how the rest of the European community doesn't have a problem
> > with it.
>
> Excuse me dude, but what do you know about "the rest of the European
> community"? I know a lot. And it uses Sendmail 8-7 bit translation, for
> the most part.
>
> Just telnet to port 25 on some European mailserver or another and ehlo.
>
> My ISP, Demon.nl, has never heard of 'ehlo'. It cannot translate 8-7 bit
> mime. Basta.


We actually do know about such things. We really don't use coal-fired
computers.

> > | I dislike hypocrites.
> > he is still standards conforming.
>
> He is not.


MMDF has a couple of corners where it does not quite fit RFC822. This
is not one of them. Note that the RFCs you are quoting are RFCs and
not standards. The standards say you should not send 8 bit
characters.

> > The 8BITMIME option in the Extended
> > SMTP protocol is totally optional.
>
> Perhaps you mean 8-bit transparent. I.e. no translation.
>
> Trouble is, that most "proper" (not English, which keeps cadgeing off
> American) European languages use above-ASCII code (look at ISO-8859).
>
> > Again go research quoted-printable
> > and base64 to see why it is not a problem at all (for standards
> > conforming systems).
>
> rfc1659


And it is which standard?

> > | I was SICK today at getting mail from one of the largest dailies
> > | (Dagbladet) in Norway that I couldn't read properly, because your mmdf
> > | server, due for death 5 years ago, chopped the data to bits. It's not
> > | just Norway, either. It's "European or not European".
>
> > How do you know that that's where the problem lies?
>
> Oh man!
>
> > What happens if
> > you try a different mailer to read the message?
>
> Ermmm Demon cuts out 8 bit transparent. Basta. Phil says it does!


It does. I wish it didn't, but that's life.

> > Maybe someone else
> > is managing an exim server that relayed the message; and maybe he set
> > the 8bitmime option. That is fully documented as not being standards
> > conforming and almost guaranteed to break stuff.
>
> No. f.ex. dagbladet.no does an mx lookup on billy.demon.nl and gets
> Demon's mailserver. Demon's mailserver accepts (which it shouldn't
> according to rfc1652) 8 bit shit for Billy and cuts out all 8-bit stuff.
> I.e. Norwegian letters.


But of course the message should not be altered by dropping the 2^7
bit from each character.

> The point is, this is am MTA that no-one else in Europe is using. It's
> CRAP. It's called mmdf.


Agreed it is horrible. We want rid of it. But it's not so simple to
remove (there are some good reasons it was chosen years ago. Or, for
the more pedantic, Demon began on SCO systems where MMDF was the
standard MTA. Even after SCO was no longer an issue, MMDF was kept
because it was, at that time, the most effective way of handling our
customer mail. There were no other MTAs which would have done the job,
and yes, a lot of time was spent looking at alternatives.

We will be converting the NL system to Exim, but it is a non-trivial
change and will take some time and a lot of testing. So I won't quote
a date.

All this is beside the point. The reality is that lots of MTA accept
non-standards compliant e-mail using 8 bit characters. And a lot of
people believe that this is the case everywhere. It is not, but, like
Microsoft products, people assume that the fact that it is common also
means that it is standard.

> Yerrrrs, but this is what is called "quoted printable" and is 7-bit. So
> no 1nder. Now ssh to a Norwegianj mail server and use Mutt or Elm or
> something on THAT server. Find a Norwegian or Danish friend or
> something. Then try it again.


If your MUA and local MTA are set up correctly, the mail will go out
with quoted printable or some other encoding. And it will pass
unharmed through every standards compliant mail system.

> No goose, this is for real.
>
> Dman, I've been in this business since 1997. Used Exim since then.
> Believe me ...
>
> > Notice how each of those characters use only 7 bits! mmdf will handle
> > this just fine, like the standards say.
>
> Yep. Do you want lessons in Norwegian, so that you can teach a couple of
> hundred thousand of the most talented IT people in the world to do it
> your way?


I can't disagree that the expectation is that all mail systems are 8
bit trnasparent and that those that aren't will have to be
replaced. But don't confuse that with a standards issue.

I am curious how some of the EBCDIC systems which still exist out
there deal with these issues. I doubt any ISPs use mainframes, but
I'll bet there are a lot of corporate systems out there that do, and
that may well have some suprises in store for those who expect that
widespread usage == standards compliance.

--
Jim Segrave           jes@???