On Mon, 9 Dec 1996, Ian Jackson wrote:
> I'd like Exim to be able to Do Something about the awfulness that is
> quoted-printable.
>
> I don't know whether Phil might have time to implement what I'm about
> to propose, but I'd like to suggest it for consideration:
The short answer is that I haven't got the time (with one small
exception - see below), at least not while I plough through the rather
long list of other features that are needed for Exim.
There is also some philosophy here. Exim is designed as an MTA that does
not offer protocol conversion services. As such it is 8-bit clean. On
receiving a message containing characters with the 8th bit set, it just
passes it on. This is tolerated behaviour from an MTA that does not
advertise 8BITMIME on input.
The amount of work needed to handle the various possibilities, if Exim
were to go in for handling all the cases, is large. I confess to having
a natural bias against it, since I think the whole 7-bit thing is
nonsense in this day and age (and was a great mistake at the start, when
TCP/IP provides 8-bit communications). I also feel that message content
should really be the province of the MUA and that an MTA should just be
passing stuff on, unless it is a gateway between different mail systems,
of course.
> The problem: the MIME RFCs specify that 8-bit messages must be mangled
> using quoted-printable if the receiving MTA doesn't support EHLO and
> advertise 8BITMIME. This is in direct opposition to what everyone was
> doing previously (just-send-8) and causes problems with eg patchfiles
> and non-MIME MUAs.
Quite. Actually, Exim sends HELO rather than EHLO at present. As it does
not use any of the facilities that EHLO provides, I saw no need to spend
time implementing the code for handling hosts that don't understand EHLO
(quite tricky, I gather; not all say "unknown command" - some drop the
connection [no prizes for guessing which software does this]).
> * Send the 8BITMIME response to EHLO. This should be settable
> independently of the settings of the other MIME-related options, and
> should be on by default.
As a result of a specific user request, I am planning to implement this,
(and only this) soon, but default it OFF. Anyone who runs Exim with the
option turned on is in some sense breaking the rules, but I understand
that it will be useful for some people.
On Mon, 9 Dec 1996, John Henders wrote:
> You can accomplist most of what you want by just adding a line to the
> source code to have exim send 8BITMIME in response to ehlo. Remember to
> put a 250- in if you insert it before the HELP printout, as otherwise it
> can cause problems with other mailers.
Quite.
> From what I understand, this is the tricky bit. The RFC requires the
> mailer to handle multipart encoding of the outgoing mail and it's
> appearantly not fun to code.
Yuck.
--
Philip Hazel University Computing Service,
ph10@??? New Museums Site, Cambridge CB2 3QG,
P.Hazel@??? England. Phone: +44 1223 334714
