This document doesn't clearly belong in either mailing list and I hate to
send to both so I've picked one.
The question has been raised about how to get people to convert
from illegal 8-bit to MIME. I thought I'd make a straw 8-to-MIME
proposal.
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"I can't understand you... try miming it"
One of the problems solved by MIME is sending ordinary text mail
in other character sets. This has been a severe problem in many
parts of the world. In the absence of any helpful standards before
MIME, users demanded and vendors supplied mail user interfaces and
intermediate mail agents which followed the Internet standards, but
allowed octets >127 in the body of the message. The way this
was presumably meant to work is as follows:
If the user was sending mail to one of his own contrymen he would
use the 8-bit mail preparation software to create and send an 8-bit
message. This would violate the standard as it passed between their
2 machines but this violation would be in accordance with a private
agreement. If the user was sending to someone in another country he
would use us-ascii and the message would thus not violate any
standards.
If this was the plan it was highly optimistic. Of course many ordinary
users did not know about the fact that sending 8-bit messages was
illegal overseas and so would be likely to use 8-bit to get to their
compatriots who are visiting overseas. Indeed the sender can't know
whether the recipient might not have set a .forward (or equivalent)
which will cause the message to be sent to a machine which can not
sensibly accept 8-bit messages. Loss of information is the very least
that is likely to happen.
The question is: now that we have lots of these machines with 8-bit
mail software how do we either get them to switch or neutralize them?
It may not be possible to get them to switch. Some places will only
use standard mail software supplied by the vendor. Even should the
vendors come out quickly with MIME software, many people have machines
that they can not or will not upgrade. Sun 386i's running SunOS 4.0.2
are an example of machines users cannot upgrade.
There is no single simple solution. We have to attack from several
directions at once.
1. Writers of SMTP servers should be encouraged to be prepared for
incoming 8-bit. In particular if it is incoming 8-bit from a host
with which they don't have a private agreement then: (a) they shouldn't
accept the message [for one thing they won't know the Character-set];
(b) They should _NOT_ bit-strip; (c) [This is more controversial] They
should arrange if possible to inform the administrator of the SMTP
client machine that her activities are illegal, perhaps by sending
her a copy of the 8-to-MIME transition document.
2. Enclaves where 8-bit has been in use should set up gateways. A
gateway has to work both ways.
2a. Machines which cannot change their software should be told that
in that case they MUST NOT send mail by following the MXs but should
configure their mail software to send all mail to the gateway. The
gateway will convert 8-bit mail from these places to MIME. It will
basically just do an encoding and add a Content-type line with the
Character-set for that host. How the gateway remembers what the
Character-set is for each host it services is a private matter. You
could use TXT RR records in the DNS and that would distribute the
job of keeping the information. However a simple table on the gateway's
file system seems easier.
2b. Hosts which don't have MIME-compatible mail readers would prefer
to have their mail come to them in 8-bit rather that q-p. To get this
service they should set their MX to point to the gateway. The gateway
will then convert MIME messages. In fact it will keep them as valid
MIME messages but change the encoding to 8-bit where possible. This
will prepare for rfc-zzzz compatibility also. The gateway will then
deliver the message to the destination host, using illegal 8-bit smtp,
over-riding the MX [some mail software will automatically say "if I
am the highest MX then I'll deliver this last hop based on the A
record"].
3. Vendors who have sold 8-bit stuff should be encouraged to: (a) deliver
the 8-to-MIME transition document to their customers; (b) deliver MIME
compatible products and stop sending illegal stuff [or at least deliver
with the 8-bit option configurable and turned off by default].
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This document recommends a pragmatic approach. People are not told
that they have to change software immediately (to MIME or to rfc-zzzz),
but are given a chance to keep working in the midst of transition.
Alternative more violent strategies might lead to resistance and to
the ultimate failure of the transition.
Bob Smart