Re: [Exim] 8bitmime?

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Author: Phil Pennock
Date:  
To: exim-users
Subject: Re: [Exim] 8bitmime?
On 2002-03-19 at 23:37 +0100, Friso Kuipers wrote:
> Visiting such a 'punt' I get:


> Doesn't even do 'ehlo'?


Correct. :^(

>                         Anyway, the real point of interest is: can I
> send a Demon customer e-mail properly encoded in say cyrillic?


Sure. Because "properly encoded" means one of:
7bit
quoted-printable
base64

8bit should not be used, because the Punt machines don't advertise
8BITMIME. If you set accept_8bitmime in an Exim configuration, and then
talk to Demon's punts or a chain of Exim machines, and then Demon's
punts, then you will have problems. Exim is not a protocol converter.
It will not downgrade the content. It won't risk all sorts of potential
attacks by trying to convert.

But if your cyrillic email is encoded such that it becomes 7bit, whether
via quoted-printable or base64 or any other encoding mutually acceptable
to both you and the intended recipient, then it will reach the far end
just fine. And this is a reasonable expectation for the Internet at
large. If a system isn't 7bit clean, then it doesn't belong on the
Internet, passing email.

There is an issue with MTAs which don't handle NULLs in the message.
Those unfortunately do exist. And never should have. If you find one,
complain. But both quoted-printable and base64 ensure that the encoded
form does not contain NULLs.

The fact that there exist MTAs which are not 8bit-clean is the reason
that the MIME stuff has all this Content-Transfer-Encoding stuff.
--
When I was younger I hated going to weddings ... it seemed that all of my
aunts and the grandmotherly types used to come up to me, poking me in the
ribs and cackling, telling me, "You're next." They stopped that crap after
I started doing the same thing to them at funerals.