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1 <?xml version="1.0" encoding="iso-2022-jp"?>
2 <!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
3 <!ENTITY rfc.number "1428">
4 <!ENTITY ja.agent "$BBeM}<T(B">
5 <!ENTITY ja.body "$BK\J8(B">
6 <!ENTITY ja.downgrade "$B3J2<$2(B">
7 <!ENTITY ja.outofband " out of band ">
8 <!ENTITY ja.protocol "$B%W%m%H%3%k(B">
9 <!ENTITY ja.upgrade "$B3J>e$2(B">
10 <!ENTITY ja.UserAgent "$BMxMQ<TBeM}<T(B">
11 <!ENTITY ja.mail.gateway "$B4XLg(B">
12 <!ENTITY ja.mail.just-send-8 "8$B%^%^Aw$j(B">
13 <!ENTITY ja.mail.mail-reader "$B%a%$%k!&%j!<%@!<(B">
14 ]>
15 <?rfc-translation show-rfc-header-category="no" ?>
16 <rfc number="&rfc.number;" category="info"
17 xmlns:myns="mailto:julian.reschke@greenbytes.de?subject=rcf2629.xslt"
18 xmlns:ja="http://suika.fam.cx/~wakaba/lang/rfc/translation/"
19 xmlns:h="http://www.w3.org/1999/xhtml">
20 <front>
21 <title abbrev="Transition to 8bit-SMTP/MIME">Transition of Internet Mail from Just-Send-8 to 8bit-SMTP/MIME</title>
22 <ja:title xml:lang="ja" abbrev="8$B%S%C%H(B SMTP/MIME $B$X$NJQ49(B">Internet $B%a%$%k$N(B&ja.mail.just-send-8;$B$+$i(B8$B%S%C%H(B SMTP/MIME $B$X$NJQ49(B</ja:title>
23 <author initials="G." surname="Vaudreuil" fullname="Greg Vaudreuil">
24 <organization abbrev="CNRI">Corporation for National Research Initiatives</organization>
25 <address>
26 <postal><street>1895 Preston White Drive, Suite 100</street>
27 <city>Reston</city><!--, --><region>VA</region> <code>22091</code>
28 <country ja:text="USA">US</country>
29 </postal>
30 <phone ja:text="(703) 620-8990">+1 703 620 8990</phone>
31 <email>GVaudre@CNRI.Reston.VA.US</email>
32 </address>
33 </author>
34 <date month="February" year="1993" />
35 <workgroup>SMTP Extensions Working Group</workgroup>
36 <abstract>
37 <t>
38 <ja:pair>
39 <ja:l xml:lang="en">
40 Protocols for extending SMTP to pass 8bit characters have been
41 defined <xref target="refs.RFC1425" /> <xref target="refs.RFC1426" />.
42 These protocols require that messages transported by
43 the extended SMTP are to be encoded in MIME
44 <xref target="refs.RFC1341" /> <xref target="refs.RFC1342" />.
45 Before work began on these protocols, several SMTP implementations
46 adopted ad-hoc mechanisms for sending 8bit data. It is desirable
47 for the extended SMTP environment and these ad hoc mechanisms
48 interoperate. This document outlines the problems in this
49 environment and an approach to minimizing the cost of transition
50 from current usage of non-MIME 8bit messages to MIME.
51 </ja:l>
52 <ja:l xml:lang="ja">
53 8$B%S%C%HJ8;z$rDL2a$5$;$k$h$&$K(B SMTP
54 $B$r3HD%$9$k(B&ja.protocol;$B$,Dj5A$5$l$F$$$^$9(B
55 <xref target="refs.RFC1425" /> <xref target="refs.RFC1426" />$B!#(B
56 $B$3$l$i$N(B&ja.protocol;$B$G$O!"3HD%(B SMTP $B$GE>Aw$5$l$k%a%C%;!<%8$,(B
57 MIME <xref target="refs.RFC1341" /> <xref target="refs.RFC1342" />
58 $B$GId9f2=$5$l$F$$$k$3$H$,I,MW$G$9!#$3$l$i$N(B&ja.protocol;$B$N:n6H$,;O$^$k0JA0!"4v$D$+$N(B
59 SMTP $B<BAu$O(B8$B%S%C%H!&%G!<%?$rAw?.$9$k$?$a$NFC@_5!9=$r:NMQ$7$F$$$^$7$?!#3HD%(B
60 SMTP $B4D6-$H$3$NMM$JFC@_5!9=$,6(D4$7$FF/$/$3$H$,K>$^$7$$$G$9!#$3$NJ8=q$O!"$3$l$i$N4D6-$G$NLdBj$H!"Hs(B MIME 8$B%S%C%H!&%a%C%;!<%8$N8=:_$NMxMQK!$+$i(B
61 MIME $B$X$NJQ49$N7PHq$N:G>.2=$NJ}K!$K$D$$$F35@b$7$^$9!#(B
62 </ja:l>
63 </ja:pair>
64 </t>
65 </abstract>
66 </front>
67 <ja:front>
68 <author fullname="$B$o$+$P(B" ja:id="wakaba">
69 <address>
70 <email>w@suika.fam.cx</email>
71 <uri>http://suika.fam.cx/~wakaba/</uri>
72 </address>
73 </author>
74 <ja:copyright>
75 <ja:item>Copyright &#xa9; $B$o$+$P(B (2002)$B!#A48"J]N1!#(B</ja:item>
76 </ja:copyright>
77 <ja:change>
78 <ja:item year="2002" month="05" day="08"><author ja:ref="wakaba" />
79 <t><ja:link type="rfc" number="2629" /> $B$G%^!<%/IU$1!#(B</t>
80 <t>$BK]Lu40N;!#(B</t>
81 </ja:item>
82 </ja:change><!-- $Date: 2002/05/09 09:52:35 $ -->
83 <h:style xml:space="preserve" type="text/css">
84 .rfc-t-artwork table
85 {margin-left: 15%; margin-right: 15%;
86 border-style: none}
87 .rfc-t-artwork table thead th
88 {border-left: thin ActiveBorder solid;
89 padding: 0.2em; text-align: left}
90 .rfc-t-artwork table thead th.css-first-child
91 {border-left-style: none}
92 .rfc-t-artwork table tbody th
93 {border-top: thin ActiveBorder solid;
94 padding: 0.2em; text-align: right; vertical-align: middle}
95 .rfc-t-artwork table tbody td
96 {border-top: thin ActiveBorder solid;
97 border-left: thin ActiveBorder solid;
98 padding: 0.2em; text-align: center; vertical-align: middle}
99 </h:style>
100 </ja:front>
101 <middle>
102
103 <section title="Terminology" ja:title-ja="$BMQ8l(B"><!-- 1. -->
104 <t>
105 <ja:pair>
106 <ja:l xml:lang="en">
107 RFC 821 defines a 7bit transport. A transport agent which does not
108 clear the high order bit upon receipt of octets with this bit set in
109 SMTP messages is called 8 bit transparent in this document. An
110 implementation of the general SMTP Extensions document
111 <xref target="refs.RFC1425" /> and the
112 8bit extensions protocol <xref target="refs.RFC1426" />
113 which passes MIME messages using all 8
114 bits of an octet is called 8bit ESMTP. An implementation of extended
115 SMTP which does not accept 8bit characters is called 7bit ESMTP. A
116 gateway is defined to be a transport agent with User Agent authority
117 to alter or convert the content of a message.
118 </ja:l>
119 <ja:l xml:lang="ja">
120 <ja:link type="rfc" number="821" /> $B$O(B8$B%S%C%HE>Aw$rDj5A$7$F$$$^$9!#(B
121 SMTP $B%a%C%;!<%8Cf$N<u$1<h$C$?%*%/%F%C%H$N:G>e0L%S%C%H$r!"$3$N%S%C%H$KCM$r@_Dj$9$k$3$H$G>C5n$7$J$$E>Aw(B&ja.agent;$B$r!"$3$NJ8=q$G$O(B8$B%S%C%HF)2a$H8F$S$^$9!#0lHL(B
122 SMTP $B3HD%J8=q(B <xref target="refs.RFC1425" /> $B5Z$S(B
123 MIME $B%a%C%;!<%8$r%*%/%F%C%H$N(B8$B%S%C%HA4$F$r;H$C$FEO$9(B8$B%S%C%H3HD%(B&ja.protocol;
124 <xref target="refs.RFC1426" /> $B$N<BAu$r(B8$B%S%C%H(B
125 ESMTP $B$H8F$S$^$9!#(B8$B%S%C%HJ8;z$r<u$1IU$1$J$$3HD%(B SMTP
126 $B$N<BAu$r(B7$B%S%C%H(B ESMTP
127 $B$H8F$S$^$9!#(B&ja.mail.gateway;$B$O!"%a%C%;!<%8$NFbMF$rJQ$($k!&JQ49$9$k(B&ja.UserAgent;$BEv6I$D$-E>Aw(B&ja.agent;$B$HDj5A$7$^$9!#(B
128 </ja:l>
129 </ja:pair>
130 </t>
131 </section>
132
133 <section title="The Problem" ja:title-ja="$BLdBjE@(B"><!-- 2. -->
134 <t>
135 <ja:pair>
136 <ja:l xml:lang="en">
137 SMTP as defined in RFC 821 limits the sending of Internet Mail to
138 US-ASCII <xref target="refs.ASCII" /> characters. As the Internet
139 has grown to include non-English correspondents, the need to
140 communicate with character sets
141 other than US-ASCII has prompted many vendors and users to extend
142 SMTP or RFC 822 to use non-ASCII character sets. Common approaches
143 are to send 7 bit national variant ISO 646 character sets over
144 current RFC822/SMTP, to extend SMTP and RFC822 to use 8bit ISO 8859
145 character sets, and to use proprietary PC character sets.
146 </ja:l>
147 <ja:l xml:lang="ja">
148 <ja:link type="rfc" number="821" /> $B$GDj5A$5$l$?(B SMTP $B$O(B
149 Internet $B%a%$%k$NAw?.$r(B US-ASCII <xref target="refs.ASCII" />
150 $BJ8;z$K@)8B$7$F$$$^$7$?!#(B Internet
151 $B$,Hs1Q8lJ8DL<T$r4^$`MM$K@.D9$9$k$K=>$$!"Hs(B US-ASCII
152 $BJ8;z=89g$K$h$k0U;WABDL$NI,MW@-$+$i!"B?$/$N@=B$<T$dMxMQ<T$,(B SMTP
153 $B$d(B <ja:link type="rfc" number="822" /> $B$rHs(B ASCII
154 $BJ8;z=89g$r;HMQ$9$k$h$&$K3HD%$7$h$&$H$7$^$7$?!#$=$N6&DL$N<jCJ$K$O(B7$B%S%C%H$N9q2HHG(B
155 ISO 646 $BJ8;z=89g$r8=9T$N(B RFC 822/SMTP $B$GAw?.$9$k(B, SMTP $B$H(B
156 RFC822 $B$r(B8$B%S%C%H$N(B ISO 8859 $BJ8;z=89g$r;HMQ$9$k$h$&$K3HD%$9$k(B,
157 $BFH@j(B PC $BJ8;z=89g$r;HMQ$9$k(B, $B$,$"$j$^$9!#(B
158 </ja:l>
159 </ja:pair>
160 </t>
161
162 <t>
163 <ja:pair>
164 <ja:l xml:lang="en">
165 A third approach is used for Japanese mail. Japanese characters are
166 represented by pairs of octets with the high order bit cleared.
167 Switching between 14 bit character sets and 7 bit character sets is
168 indicated within the message by ISO 2022 escape sequences.
169 </ja:l>
170 <ja:l xml:lang="ja">
171 $B;0HVL\$NJ}K!$OF|K\8l%a%$%k$K;H$o$l$F$$$^$9!#F|K\8lJ8;z$O:G>e0L%S%C%H$,>C5n$5$l$?%*%/%F%C%H$NAH9g$;$GI=8=$7$^$9!#(B14$B%S%C%HJ8;z=89g$H(B7$B%S%C%HJ8;z=89g$O%a%C%;!<%8Cf$G$O(B
172 ISO 2022 $B%(%9%1!<%WNs$G@Z$jBX$($^$9!#(B
173 </ja:l>
174 </ja:pair>
175 </t>
176 <ja:note>
177 <t>$B;0HVL\$NJ}K!$H$O!VFH@j(B PC $BJ8;z=89g$N;HMQ!W$G$9$+$i!"$3$N@bL@$G$O9gCW$7$^$;$s!#$*$=$i$/!";0HVL\$NJ}K!$O!"!V0lHVL\!&FsHVL\0J30$NJ}K!!W$H$G$b$7$?$+$C$?$N$G$7$g$&!#(B</t>
178 </ja:note>
179
180 <t>
181 <ja:pair>
182 <ja:l xml:lang="en">
183 So long as these implementations can communicate without intermediate
184 transformations and have a loose private agreement on the use of a
185 specific character set without tagging, basic mail service can be
186 provided.
187 </ja:l>
188 <ja:l xml:lang="ja">
189 $B$3$l$i$N<BAu$OESCf7PO)$G$NJQ7AL5$7$KDL?.=PMh!"FCDjJ8;z=89g$N;%L5$7$G$N;HMQ$N4K$$;dE*$J9g0U$,$"$k$N$G!"4pK\E*$J%a%$%k!&%5!<%S%9$,Ds6!=PMh$^$9!#(B
190 </ja:l>
191 </ja:pair>
192 </t>
193
194 <t>
195 <ja:pair>
196 <ja:l xml:lang="en">
197 In the transition to the negotiated 8bit ESMTP/MIME environment, it
198 is important that mail sent by a currently non-conforming user can be
199 read by another non-conforming user. This existing functionality is
200 reduced by conversion from 8bit text to text encoded in unreadable
201 Base-64 or "garbled" text encoded in quoted printable.
202 </ja:l>
203 <ja:l xml:lang="ja">
204 $B@^>W(B8$B%S%C%H(B ESMTP/MIME
205 $B4D6-$X$NJQ49$G!"8=:_HsE,9g$NMxMQ<T$,Aw?.$7$?%a%$%k$OB>$NHsE,9g$NMxMQ<T$,FI$`$3$H$,=PMh$k$3$H$O=EMW$G$9!#$3$N4{B85!G=@-$O!"(B8$B%S%C%HJ8$+$iIT2DFI(B
206 Base-64 $B$GId9f2=$5$l$?J8$d(B quoted printable
207 $B$GId9f2=$5$l$?!VJ8;z2=$1$7$?!WJ8$KJQ49$9$k$3$H$G8:>/$7$^$9!#(B
208 </ja:l>
209 </ja:pair>
210 </t>
211
212 <t>
213 <ja:pair>
214 <ja:l xml:lang="en">
215 There are several interesting non-interoperable cases that currently
216 exist in non US-ASCII mail and several new ones likely to emerge in a
217 transition to 8bit/MIME. Below is a listing of the
218 transition-to-mime cases. Only solutions to <xref target="s2.i4" />
219 in the context of a translating gateway are discussed in this memo.
220 </ja:l>
221 <ja:l xml:lang="ja">
222 $B8=:_Hs(B US-ASCII $B%a%$%k$KB8:_$9$k6=L#?<$$Aj8_DL?.IT2D$J;vNc!"$"$k$$$O(B8$B%S%C%H(B/MIME
223 $B$X$NJQ49$GIb>e$7$=$&$J?7$7$$;vNc$,4v$D$+$"$j$^$9!#2<$K5s$2$k$N$O!"(B
224 MIME $B$X$NJQ49$N;vNc$G$9!#JQ49(B&ja.mail.gateway;$B$K$*$1$k(B
225 <xref target="s2.i4" /> $B$N2r7h:v$N$_$r$3$N%a%b$G$O<h$j>e$2$^$9!#(B
226 </ja:l>
227 </ja:pair>
228 </t>
229
230 <figure>
231 <ja:pair>
232 <ja:l xml:lang="en">
233 <ja:artwork>
234 <artwork>
235 \ Receiver
236 \ 7bit 8bit MIME/
237 Sender \| only | transparent | ESMTP
238 ----------------------------------------
239 7bit only | (1) | (1) | (1)
240 ----------------------------------------
241 8bit transparent | (2) | (3) | (4)
242 ----------------------------------------
243 MIME/ESMTP | (5) | (5) | (6)
244 </artwork>
245 <h:table>
246 <h:thead>
247 <h:tr>
248 <h:th class="css-first-child">Sender\Receiver</h:th>
249 <h:th>7bit only</h:th>
250 <h:th>8bit transparent</h:th><h:th>MIME/ESMTP</h:th>
251 </h:tr>
252 </h:thead>
253 <h:tbody>
254 <h:tr>
255 <h:th>7bit only</h:th>
256 <h:td><xref target="s2.i1" /></h:td>
257 <h:td><xref target="s2.i1" /></h:td>
258 <h:td><xref target="s2.i1" /></h:td>
259 </h:tr>
260 <h:tr>
261 <h:th>8bit transparent</h:th>
262 <h:td><xref target="s2.i2" /></h:td>
263 <h:td><xref target="s2.i3" /></h:td>
264 <h:td><xref target="s2.i4" /></h:td>
265 </h:tr>
266 <h:tr>
267 <h:th>MIME/ESMTP</h:th>
268 <h:td><xref target="s2.i5" /></h:td>
269 <h:td><xref target="s2.i5" /></h:td>
270 <h:td><xref target="s2.i6" /></h:td>
271 </h:tr>
272 </h:tbody>
273 </h:table>
274 </ja:artwork>
275 </ja:l>
276 <ja:l xml:lang="ja">
277 <ja:artwork>
278 <h:table>
279 <h:thead>
280 <h:tr>
281 <h:th class="css-first-child">$BAw?.<T(B\$B<u?.<T(B</h:th>
282 <h:th>7$B%S%C%H$N$_(B</h:th>
283 <h:th>8$B%S%C%HF)2a(B</h:th><h:th>MIME/ESMTP</h:th>
284 </h:tr>
285 </h:thead>
286 <h:tbody>
287 <h:tr>
288 <h:th>7$B%S%C%H$N$_(B</h:th>
289 <h:td><xref target="s2.i1" /></h:td>
290 <h:td><xref target="s2.i1" /></h:td>
291 <h:td><xref target="s2.i1" /></h:td>
292 </h:tr>
293 <h:tr>
294 <h:th>8$B%S%C%HF)2a(B</h:th>
295 <h:td><xref target="s2.i2" /></h:td>
296 <h:td><xref target="s2.i3" /></h:td>
297 <h:td><xref target="s2.i4" /></h:td>
298 </h:tr>
299 <h:tr>
300 <h:th>MIME/ESMTP</h:th>
301 <h:td><xref target="s2.i5" /></h:td>
302 <h:td><xref target="s2.i5" /></h:td>
303 <h:td><xref target="s2.i6" /></h:td>
304 </h:tr>
305 </h:tbody>
306 </h:table>
307 </ja:artwork>
308 </ja:l>
309 </ja:pair>
310 </figure>
311
312 <list style="hanging">
313 <t hangText="(1)" ja:anchor="s2.i1">
314 <ja:pair>
315 <ja:l xml:lang="en">7Bit non-MIME sender to 7bit, MIME, or
316 8bit transparent receiver</ja:l>
317 <ja:l xml:lang="ja">7$B%S%C%HHs(B MIME $BAw?.<T$+$i(B7$B%S%C%H$^$?$O(B
318 MIME, 8$B%S%C%HF)2a<u?.<T$X(B</ja:l>
319 </ja:pair>
320 <vspace breakLines="1" />
321 <ja:pair>
322 <ja:l xml:lang="en">
323 This will continue to work unchanged with nationally varient ISO
324 646 or ISO 2022 character set shifting if an external "out of
325 band" agreement exists between the sender and the receiver. A
326 7bit to 8bit/ESMTP gateway need not alter the content of this
327 message.
328 </ja:l>
329 <ja:l xml:lang="ja">
330 ISO 646 $B9q2HHG$d(B ISO 2022 $BJ8;z=89gE>0\$r!"30It!V(B&ja.outofband;$B!W9g0U$,Aw<u?.<T4V$GB8:_$9$k>l9g$OJQ99L5$/1?MQ$7B3$1$^$9!#(B7$B%S%C%H$+$i(B8$B%S%C%H(B/SMTP
331 $B$X$N(B&ja.mail.gateway;$B$O$3$N%a%C%;!<%8$NFbMF$rJQ$($kI,MW$O$"$j$^$;$s!#(B
332 </ja:l>
333 </ja:pair>
334 </t>
335 <ja:note>
336 <t>Jargon File $B$K$O!"(B $B!V(Bout of band$B!W(B =
337 <h:q title="Jargon File $B$+$i!V(Bout of band$B!W(B" xml:lang="en">sometimes
338 used to describe what communications people call $B!F(Bshift characters$B!G(B,
339 such as the <h:code>ESC</h:code> that leads control sequences for
340 many terminals</h:q> $B$H=q$+$l$F$$$^$9!#(B</t>
341 </ja:note>
342
343 <t hangText="(2)" ja:anchor="s2.i2">
344 <ja:pair>
345 <ja:l xml:lang="en">8bit sender to 7bit non-MIME receiver</ja:l>
346 <ja:l xml:lang="ja">8$B%S%C%HAw?.<T$+$i(B7$B%S%C%HHs(B MIME $B<u?.<T$X(B</ja:l>
347 </ja:pair>
348 <vspace breakLines="1" />
349 <ja:pair>
350 <ja:l xml:lang="en">
351 The receiver will receive bit-stripped mail which results in the
352 mis-interpretation of the data and the wrong character being
353 displayed or printed. Mail sent using languages where most
354 characters are in the US-ASCII subset of ISO 8859 may be somewhat
355 readable.
356 </ja:l>
357 <ja:l xml:lang="ja">
358 $B<u?.<T$O!"%G!<%?$N8m2r<a$N7k2L$?$k%S%C%HMn$A%a%$%k$r<u$1<h$j!"4V0c$C$?J8;z$,I=<(!&0u:~$5$l$k$3$H$K$J$k$G$7$g$&!#$[$H$s$I$NJ8;z$,(B
359 ISO 8859 $B$N(B US-ASCII $BItJ,=89gCf$K$"$k8@8l$r;H$C$FAw$i$l$?%a%$%k$O$=$l$J$j$KFI$a$k$+$b$7$l$^$;$s!#(B
360 </ja:l>
361 </ja:pair>
362 </t>
363
364 <t hangText="(3)" ja:anchor="s2.i3">
365 <ja:pair>
366 <ja:l xml:lang="en">8bit transparent sender to 8bit transparent receiver</ja:l>
367 <ja:l xml:lang="ja">8$B%S%C%HF)2aAw?.<T$+$i(B8$B%S%C%HF)2a<u?.<T$X(B</ja:l>
368 </ja:pair>
369 <vspace breakLines="1" />
370 <ja:pair>
371 <ja:l xml:lang="en">
372 Will work if an external agreement "out of band" to use a
373 particular character set without tagging exists between the sender
374 and the receiver.
375 </ja:l>
376 <ja:l xml:lang="ja">
377 $BFCDjJ8;z=89g$r;%L5$7$G;HMQ$9$k30It9g0U!V(B&ja.outofband;$B!W$,Aw<u?.4V$KB8:_$9$k>l9g$O$&$^$/F/$/$G$7$g$&!#(B
378 </ja:l>
379 </ja:pair>
380 </t>
381
382 <t hangText="(4)" ja:anchor="s2.i4">
383 <ja:pair>
384 <ja:l xml:lang="en">8bit transparent sender to MIME/ESMTP conformant receiver</ja:l>
385 <ja:l xml:lang="ja">8$B%S%C%HF)2aAw?.<T$+$i(B MIME/ESMTP $BE,9g<u?.<T$X(B</ja:l>
386 </ja:pair>
387 <vspace breakLines="1" />
388 <ja:pair>
389 <ja:l xml:lang="en">
390 Will work if a reasonable upgrade path is provided via gateways,
391 the indicated character set tag inserted by the gateway is correct
392 and the receiver supports the character set chosen by the sender.
393 This case is the focus of this memo.
394 </ja:l>
395 <ja:l xml:lang="ja">
396 $BJ,JL$"$k3J>e$27PO)$,(B&ja.mail.gateway;$B7PM3$GDs6!$5$l$F$$$F!"(B&ja.mail.gateway;$B$,A^F~$9$kJ8;z=89g;%$,@5$7$/$F!"<u?.<T$,Aw?.<T$NA*$s$@J8;z=89g$KBP1~$7$F$$$l$P!"$&$^$/F/$-$^$7$g$&!#$3$N>l9g$,$3$N%a%b$N>GE@$G$9!#(B
397 </ja:l>
398 </ja:pair>
399 </t>
400
401 <t hangText="(5)" ja:anchor="s2.i5">
402 <ja:pair>
403 <ja:l xml:lang="en">MIME/ESMTP sender to non-MIME 7bit receiver</ja:l>
404 <ja:l xml:lang="ja">MIME/ESMTP $BAw?.<T$+$iHs(B MIME 7$B%S%C%H<u?.<T$X(B</ja:l>
405 </ja:pair>
406 <vspace breakLines="1" />
407 <ja:pair>
408 <ja:l xml:lang="en">
409 Because the ESMTP/MIME sender cannot know if the receiver will
410 understand 8bits, the sender will encode the text into base-64 or
411 quoted-printable which may be considered "garbled" by the
412 receiver. To provide a useful downgrade path the gateway must
413 have some knowledge about the capabilities of the receiver. When
414 the character set can be clearly identified, techniques like the
415 menmonic MNEM encoding described in RFC 1345 may be helpful in
416 this case.
417 </ja:l>
418 <ja:l xml:lang="ja">
419 ESMTP/MIME $BAw?.<T$O<u?.<T$,(B8$B%S%C%H$rM}2r$9$k$+$I$&$+CN$jF@$J$$$N$G!"Aw?.<T$OJ8$r(B
420 base-64 $B$+<u?.<T$K!VJ8;z2=$1$7$?!W$H;W$o$l$k$+$b$7$l$J$$(B
421 quoted-printable
422 $B$GId9f2=$9$k$G$7$g$&!#M-MQ$J3J2<$27PO)$rDs6!$9$k$K$O(B&ja.mail.gateway;$B$O<u?.<T$NM}2rG=NO$K$D$$$F$NCN<1$rM-$9$kI,MW$,$"$j$^$9!#J8;z=89g$,L@3N$K<1JL=PMh$k;~$O!"(B
423 <ja:link type="rfc" number="1345" /> $B$G@bL@$5$l$F$$$k5-K!(B MNEM
424 $BId9f2=$NMM$J<jK!$,$3$N>l9g$K$OM-MQ$+$b$7$l$^$;$s!#(B
425 </ja:l>
426 </ja:pair>
427 </t>
428
429 <t hangText="(6)" ja:anchor="s2.i6">
430 <ja:pair>
431 <ja:l xml:lang="en">MIME/ESMTP sender to MIME/ESMTP receiver</ja:l>
432 <ja:l xml:lang="ja">MIME/ESMTP $BAw?.<T$+$i(B MIME/ESMTP $B<u?.<T$X(B</ja:l>
433 </ja:pair>
434 <vspace breakLines="1" />
435 <ja:pair>
436 <ja:l xml:lang="en">
437 Interoperability will be attained provided the receiver supports
438 the character set chosen by the sender.
439 </ja:l>
440 <ja:l xml:lang="ja">$BAj8_DL?.@-$OAw?.<T$,A*Br$7$?J8;z=89g$K<u?.<T$,BP1~$9$k$3$H$K$h$jK~$?$5$l$^$9!#(B</ja:l>
441 </ja:pair>
442 </t>
443 </list>
444 </section>
445
446 <section title="Upgrade Path from 8bit Transparent to ESMTP/MIME"
447 ja:title-ja="8$B%S%C%HF)2a$+$i(B ESMTP/MIME $B$X$N(B&ja.upgrade;$B7PO)(B"><!-- 3. -->
448
449 <t>
450 <ja:pair>
451 <ja:l xml:lang="en">
452 A gateway which has been upgraded to support Extended SMTP may
453 upgrade an 8bit message received to MIME. This is consistent with
454 the requirement that all 8bit mail sent by ESMTP be encoded in MIME.
455 The upgrade should be done using the best available information.
456 </ja:l>
457 <ja:l xml:lang="ja">
458 $B3HD%(B SMTP
459 $B$KBP1~$9$k$h$&(B&ja.upgrade;$B$9$k(B&ja.mail.gateway;$B$O!"<u?.$7$?(B8$B%S%C%H!&%a%C%;!<%8$r(B
460 MIME $B$K(B&ja.upgrade;$B$7$F9=$$$^$;$s!#$3$l$O(B ESMTP
461 $B$GAw?.$5$l$k(B8$B%S%C%H!&%a%$%k$OA4$F(B
462 MIME $B$GId9f2=$5$l$F$$$J$1$l$P$J$i$J$$$H$$$&MW7o$rK~$?$7$^$9!#(B&ja.upgrade;$B$O0lHVMxMQ2DG=$J>pJs$r;H$C$F9T$&$Y$-$G$9!#(B
463 </ja:l>
464 </ja:pair>
465 </t>
466
467 <t>
468 <ja:pair>
469 <ja:l xml:lang="en">
470 A site may "upgrade" to MIME en-masse by implementing MIME conversion
471 for all messages leaving the site. For text messages, the body can
472 be converted by adding a MIME-version header and a Content-Type:
473 Text/Plain with the character set in use in the site, provided the
474 site uses a single character set.
475 </ja:l>
476 <ja:l xml:lang="ja">
477 $B%5%$%H$O!"%5%$%H$rN%$l$kA4$F$N%a%C%;!<%8$r!"(B
478 MIME $B$r<BAu$9$k$3$H$G$^$H$a$F(B MIME $B$K!V(B&ja.upgrade;$B!W$7$F$b9=$$$^$;$s!#%F%-%9%H!&%a%C%;!<%8$K$D$$$F$O!"(B&ja.body;$B$O(B
479 MIME-version $BF,$H(B Content-Type: Text/Plain
480 $B$K%5%$%HFb$G;H$o$l$F$$$kJ8;z=89g$r$D$1$k$3$H$G!"%5%$%H$,C10lJ8;z=89g$r;H$C$F$$$k>l9g$OJQ49=PMh$^$9!#(B
481 </ja:l>
482 </ja:pair>
483 </t>
484
485 <t>
486 <ja:pair>
487 <ja:l xml:lang="en">
488 An appropriate Content-Transfer-Encoding header line must be added to
489 indicate any encoding that may be necessary.
490 </ja:l>
491 <ja:l xml:lang="ja">
492 $BE,@Z$J(B Content-Transfer-Encoding
493 $BF,9T$r!"I,MW$+$b$7$l$J$$Id9f2=$r<($9$N$K2C$($J$1$l$P$J$j$^$;$s!#(B
494 </ja:l>
495 </ja:pair>
496 </t>
497
498 <!--
499 Example:
500 --><ja:example xml:space="preserve">
501 MIME-Version: 1.0
502 Content-Type: Text/Plain; Charset = ISO-8859-1
503 Content-Transfer-Encoding: 8bit
504 </ja:example>
505
506 <t>
507 <ja:pair>
508 <ja:l xml:lang="en">
509 If no information about the character set in use is available, the
510 gateway should upgrade the content by using the character set
511 "unknown-8bit". The unknown-8bit value of the charset parameter
512 indicates only that no reliable information about the character
513 set(s) used in the message was available.
514 </ja:l>
515 <ja:l xml:lang="ja">
516 $B;HMQ$5$l$F$$$kJ8;z=89g$K$D$$$F$N>pJs$,L5$$>l9g$O!"(B&ja.mail.gateway;$B$OFbMF$rJ8;z=89g(B
517 "unknown-8bit" $B$r;H$C$F(B&ja.upgrade;$B$9$k$Y$-$G$9!#(B charset
518 $B%Q%i%a!<%?!<$N(B unknown-8bit
519 $BCM$O%a%C%;!<%8$K;H$o$l$F$$$kJ8;z=89g$K$D$$$F$N3N<B$J>pJs$rF@$k$3$H$,=PMh$J$+$C$?$3$H$N$_$r<($7$^$9!#(B
520 </ja:l>
521 </ja:pair>
522 </t>
523
524 <t>
525 <ja:pair>
526 <ja:l xml:lang="en">
527 If a message body has been upgraded to MIME, the RFC 822 headers
528 containing non US-ASCII characters must be upgraded to conform with
529 the header encoding rules of RFC1342. A gateway should recode all
530 unstructered header fields as well as RFC 822 "comment"s and
531 "phrase"s according to the rules of RFC 1342. There is no equivalent
532 in RFC 1342 to the "8bit" Content-Transfer-Encoding value for message
533 bodies so all 8bit header text must be transformed according to
534 either the "B" or the "Q" encoding method. For ISO 8859 character
535 sets, the "Q" encoding will generally result in somewhat readable
536 headers.
537 </ja:l>
538 <ja:l xml:lang="ja">
539 $B%a%C%;!<%8(B&ja.body;$B$,(B MIME $B$K(B&ja.upgrade;$B$5$l$k>l9g!"Hs(B US-ASCII
540 $BJ8;z$r4^$`(B <ja:link type="rfc" number="822" /> $BF,$O(B
541 RFC 1342
542 $B$NF,Id9f2=5,B'$KE,9g$9$k$h$&(B&ja.upgtade;$B$7$J$1$l$P$J$j$^$;$s!#(B&ja.mail.gateway;$B$OA4$F$NHs9=B$2=F,NN0h$H(B
543 RFC 822 "comment" $B$H(B "phrase" $B$r(B RFC 1342
544 $B$N5,B'$K=>$$:FId9f2=$9$k$Y$-$G$9!#%a%C%;!<%8(B&ja.body;$B$N(B "8bit"
545 $BFbMFE>AwId9f2=CM$KAjEv$9$k$b$N$O(B RFC 1342
546 $B$K$OL5$$$N$G!"A4$F$N(B8$B%S%C%HF,J8$O(B "B" $BId9f2=J}<0$^$?$O(B "Q"
547 $BId9f2=J}<0$GId9f2=$7$J$1$l$P$J$j$^$;$s!#(B ISO 8859 $BJ8;z=89g$K$O!"(B
548 "Q" $BId9f2=$r;H$&$H!"DL>o$d$d2DFI$JF,$H$J$j$^$9!#(B
549 </ja:l>
550 </ja:pair>
551 </t>
552
553 <figure>
554 <preamble>
555 <ja:pair>
556 <ja:l xml:lang="en">
557 Trace information should be added to the document with a convert
558 clause: "rfc822-to-8bit", "rfc822-to-base-64" or "rfc822-to-quoted-
559 printable" e.g.,
560 </ja:l>
561 <ja:l xml:lang="ja">
562 $BDI@W>pJs$r<!$NNc$N$h$&$KJQ49(B (convert) $B>r9`(B "rfc822-to-8bit",
563 "rfc822-to-base-64", "rfc822-to-quoted-printable"
564 $B$D$-$GJ8=q$KDI2C$9$k$Y$-$G$9!#(B
565 </ja:l>
566 </ja:pair>
567 </preamble>
568
569 <artwork xml:space="preserve">
570 Received: from dbc.mtview.ca.us by dbc.mtview.ca.us
571 convert rfc822-to-8bit; Tue, 01 Sep 1992 01:18:00 -0700
572 </artwork>
573 </figure>
574 </section>
575
576 <section title="Appendix $B!=(B The &quot;unknown-8bit&quot; Character Set"
577 ja:title-ja="$BImB0=q(B $B!=(B &quot;unknown-8bit&quot; $BJ8;z=89g(B"
578 myns:unnumbered="yes">
579
580 <t>
581 <ja:pair>
582 <ja:l xml:lang="en">
583 This section defines a "charset" parameter, for use in a MIME
584 Content-Type field.
585 </ja:l>
586 <ja:l xml:lang="ja">
587 $B$3$N@a$G$O(B MIME Content-Type $BNN0h$G;H$&(B "charset"
588 $B%Q%i%a!<%?!<$rDj5A$7$^$9!#(B
589 </ja:l>
590 </ja:pair>
591 </t>
592
593 <t>
594 <ja:pair>
595 <ja:l xml:lang="en">
596 A special purpose character set called "unknown-8bit" is defined to
597 be an unknown 8bit character set, encoded into a sequence of octets.
598 It can be used as a label for any character set from any language,
599 using any encoding. It must not be further defined.
600 </ja:l>
601 <ja:l xml:lang="ja">
602 "unknown-8bit"
603 $B$H$$$&FC<lL\E*J8;z=89g$r!"%*%/%F%C%HNs$KId9f2=$5$l$?L$CN$N(B8$B%S%C%HJ8;z=89gMQ$KDj5A$7$^$9!#$3$l$O$$$+$J$k8@8l$G$$$+$J$kId9f2=$rMQ$$$k$$$+$J$kJ8;z=89g$K$b;%$H$7$F;H$&$3$H$,=PMh$^$9!#$3$l0J>e$ODj5A$7$^$;$s!#(B
604 </ja:l>
605 </ja:pair>
606 </t>
607
608 <t>
609 <ja:pair>
610 <ja:l xml:lang="en">
611 The use of this token in a "charset=" field of a message indicates
612 that nothing is known about the character set used. This marker is
613 intended for use by non-MIME to MIME gateways; specifically in those
614 which translate from SMTP to 8bit ESMTP/MIME.
615 </ja:l>
616 <ja:l xml:lang="ja">
617 $B$3$N;z6g$r%a%C%;!<%8$N(B "charset="
618 $BNN0h$G;H$&$3$H$G!";H$o$l$F$$$kJ8;z=89g$K$D$$$FA4$/$b$C$FITL@$G$"$k$3$H$r<($7$^$9!#$3$N0u$OHs(B
619 MIME $B$+$i(B MIME $B$X$N(B&ja.mail.gateway;$B!"6qBNE*$K$O(B SMTP
620 $B$+$i(B8$B%S%C%H(B ESMTP/MIME
621 $B$KJQ49$9$k(B&ja.mail.gateway;$B$G;H$&$3$H$r0U?^$7$F$$$^$9!#(B
622 </ja:l>
623 </ja:pair>
624 </t>
625
626 <t>
627 <ja:pair>
628 <ja:l xml:lang="en">
629 This character set is not intended to be used by mail composers.
630 It is assumed that the mail composer knows the character set in
631 use and will mark it with a character set value as specified in
632 <xref target="refs.RFC1341" />, as amended by current Assigned
633 Numbers documents <xref target="refs.STD2" />.
634 </ja:l>
635 <ja:l xml:lang="ja">
636 $B$3$NJ8;z=89g$O%a%$%k:n@.<T$,;H$&$3$H$O0U?^$7$F$$$^$;$s!#%a%$%k:n@.<T$O;HMQ$9$kJ8;z=89g$rCN$C$F$$$F!"(B
637 <xref target="refs.RFC1341" /> $B$G5,Dj$5$l$F8=9T$N3dEvHV9fJ8=q(B
638 <xref target="refs.STD2" />
639 $B$G2~D{$5$l$?J8;z=89gCM$G0u$r$D$1$k$HA[Dj$7$F$$$^$9!#(B
640 </ja:l>
641 </ja:pair>
642 </t>
643
644 <t>
645 <ja:pair>
646 <ja:l xml:lang="en">
647 The use of the "unknown-8bit" label is intended only by mail gateway
648 agents which cannot determine via out-of-band information the
649 intended character set.
650 </ja:l>
651 <ja:l xml:lang="ja">
652 "unknown-8bit"
653 $B;%$N;HMQ$O!"(B&ja.outofband;$B>pJs$K$h$j0U?^$5$l$?J8;z=89g$r7hDj=PMh$J$$%a%$%k(B&ja.mail.gateway;&ja.agent;$B$K$h$j$N$_;H$o$l$k$3$H$rA[Dj$7$F$$$^$9!#(B
654 </ja:l>
655 </ja:pair>
656 </t>
657
658 <t>
659 <ja:pair>
660 <ja:l xml:lang="en">
661 The interpretation of the "unknown-8bit" is up to the mail reader.
662 It is assumed that in many cases the human user will be able to
663 interpret the information and choose an appropriate character set or
664 pre-processor.
665 </ja:l>
666 <ja:l xml:lang="ja">
667 "unknown-8bit"
668 $B$N2r<a$O(B&ja.mail.mail-reader;$B$K0Q$M$i$l$^$9!#B?$/$N>l9g$G$O?M4VMxMQ<T$,>pJs$r2r<a$7$FE,@Z$JJ8;z=89g$"$k$$$OA0=hM}4o$rA*Br$G$-$k$H;W$o$l$^$9!#(B
669 </ja:l>
670 </ja:pair>
671 </t>
672
673 </section>
674
675 <section title="Acknowledgements" myns:unnumbered="yes">
676 <t>
677 <ja:pair>
678 <ja:l xml:lang="en">
679 This document originated as a hallway conversation between
680 Ned Freed, Neil Katin, and the author. Substantive input
681 was received from Jonathan Laventhol, Craig Everhart,
682 Olle Jarnefors, and Olafur Gudmundsson. The document was
683 refined with the input of many participants in the IETF SMTP
684 Extensions Working Group.
685 </ja:l>
686 <ja:l xml:lang="ja">
687 $B$3$NJ8=q$O(B Ned Freed, Neil Katin $B$HCx<T$N0f8MC<2q5D$+$i@8$^$l$^$7$?!#(B
688 Jonathan Laventhol, Craig Everhart,
689 Olle Jarnefors, Olafur Gudmundsson
690 $B$,:2$r?a$-9~$s$G$/$l$^$7$?!#$3$NJ8=q$O(B
691 IETF SMTP $B3HD%:n6HIt2q$N;22C<T$N0U8+$K$h$j@:O#$5$l$^$7$?!#(B
692 </ja:l>
693 </ja:pair>
694 </t>
695 </section>
696
697 <ja:insert section="references" />
698
699
700 <section title="Security Considerations" myns:unnumbered="yes">
701 <t>Security issues are not discussed in this memo.</t>
702 </section>
703
704 </middle>
705 <back>
706 <references>
707 <reference anchor="refs.RFC1341"><!-- [1] -->
708 <front><title>Multipurpose Internet Mail Extensions</title>
709 <ja:title xml:lang="ja">$BB?L\E*(B Internet $B%a%$%k3HD%(B</ja:title>
710 <author initials="N." surname="Borenstein">
711 <organization>Bellcore</organization>
712 </author>
713 <author initials="N." surname="Freed">
714 <organization>Innosoft</organization>
715 </author>
716 <date month="June" year="1992" />
717 </front>
718 <seriesInfo name="RFC" value="1341" />
719 </reference>
720 <reference anchor="refs.RFC1342"><!-- [2] -->
721 <front><title>Representation of Non-ASCII Text in
722 Internet Message Headers</title>
723 <ja:title xml:lang="ja">$BHs(B ASCII $BJ8$N(B Internet
724 $B%a%C%;!<%8F,$K$*$1$kI=8=(B</ja:title>
725 <author initials="K." surname="Moore">
726 <organization>University of Tennessee</organization>
727 </author>
728 <date month="June" year="1992" />
729 </front>
730 <seriesInfo name="RFC" value="1342" />
731 </reference>
732 <reference anchor="refs.RFC1425"><!-- [3] -->
733 <front><title>SMTP Service Extensions</title>
734 <ja:title xml:lang="ja">SMTP $B%5!<%S%93HD%(B</ja:title>
735 <author initials="J." surname="Klensin" ja:text="Klensin, J., WG Chair">
736 <organization>United Nations University</organization>
737 </author>
738 <author initials="N." surname="Freed" ja:text="Freed, N., Editor">
739 <organization>Innosoft International, Inc.</organization>
740 </author>
741 <author initials="M." surname="Rose">
742 <organization>Dover Beach Consulting, Inc.</organization>
743 </author>
744 <author initials="E." surname="Stefferud">
745 <organization>Network Management Associates, Inc.</organization>
746 </author>
747 <author initials="D." surname="Crocker">
748 <organization>The Branch Office</organization>
749 </author>
750 <date month="February" year="1993" />
751 </front>
752 <seriesInfo name="RFC" value="1425" />
753 </reference>
754 <reference anchor="refs.RFC1426"><!-- [4] -->
755 <front><title>SMTP Service Extensions for 8bit
756 MIMEtransport</title>
757 <ja:title xml:lang="ja">8$B%S%C%H(B MIME $BE>AwMQ(B
758 SMTP $B%5!<%S%93HD%(B</ja:title>
759 <author initials="J." surname="Klensin" ja:text="Klensin, J., WG Chair">
760 <organization>United Nations University</organization>
761 </author>
762 <author initials="N." surname="Freed" ja:text="Freed, N., Editor">
763 <organization>Innosoft International, Inc.</organization>
764 </author>
765 <author initials="M." surname="Rose">
766 <organization>Dover Beach Consulting, Inc.</organization>
767 </author>
768 <author initials="E." surname="Stefferud">
769 <organization>Network Management Associates, Inc.</organization>
770 </author>
771 <author initials="D." surname="Crocker">
772 <organization>The Branch Office</organization>
773 </author>
774 <date month="February" year="1993" />
775 </front>
776 <seriesInfo name="RFC" value="1426" />
777 </reference>
778 <reference anchor="refs.ASCII"><!-- [5] -->
779 <front><title>Coded Character Set$B!=!=(B7-Bit American Standard Code
780 for Information Interchange</title>
781 <ja:title xml:lang="ja">$BId9f2=J8;z=89g!=!=(B7$B%S%C%H$N>pJs8r49MQ0!JFMx2CI8=`Id9f(B</ja:title>
782 </front>
783 <seriesInfo name="ANSI" value="X3.4-1986" />
784 </reference>
785 <reference anchor="refs.STD2"><!-- [6] -->
786 <front><title>Assigned Numbers</title>
787 <ja:title xml:lang="ja">$B3dEvHV9f(B</ja:title>
788 <author initials="J." surname="Reynolds">
789 <organization>USC/Information Sciences Institute</organization>
790 </author>
791 <author initials="J." surname="Postel">
792 <organization>USC/Information Sciences Institute</organization>
793 </author>
794 <date month="July" year="1992" />
795 </front>
796 <seriesInfo name="STD" value="2" />
797 <seriesInfo name="RFC" value="1340" />
798 </reference>
799 </references>
800 </back>
801 </rfc>

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