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Contents of /doc/rfc-ja/rfc1428-ja.rfcja

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Revision 1.4 - (show annotations) (download)
Sat Sep 13 08:57:55 2003 UTC (20 years, 7 months ago) by wakaba
Branch: MAIN
CVS Tags: HEAD
Changes since 1.3: +11 -9 lines
Some markup fixes to be valid

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: 2002/09/01 09:18:48 $ -->
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 <t>
313 <list style="hanging">
314 <t hangText="(1)" ja:anchor="s2.i1">
315 <ja:pair>
316 <ja:l xml:lang="en">7Bit non-MIME sender to 7bit, MIME, or
317 8bit transparent receiver</ja:l>
318 <ja:l xml:lang="ja">7$B%S%C%HHs(B MIME $BAw?.<T$+$i(B7$B%S%C%H$^$?$O(B
319 MIME, 8$B%S%C%HF)2a<u?.<T$X(B</ja:l>
320 </ja:pair>
321 <vspace blankLines="1" />
322 <ja:pair>
323 <ja:l xml:lang="en">
324 This will continue to work unchanged with nationally varient ISO
325 646 or ISO 2022 character set shifting if an external "out of
326 band" agreement exists between the sender and the receiver. A
327 7bit to 8bit/ESMTP gateway need not alter the content of this
328 message.
329 </ja:l>
330 <ja:l xml:lang="ja">
331 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
332 $B$X$N(B&ja.mail.gateway;$B$O$3$N%a%C%;!<%8$NFbMF$rJQ$($kI,MW$O$"$j$^$;$s!#(B
333 </ja:l>
334 </ja:pair>
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$$$^$9!#(B</t>
341 </ja:note>
342 </t>
343
344 <t hangText="(2)" ja:anchor="s2.i2">
345 <ja:pair>
346 <ja:l xml:lang="en">8bit sender to 7bit non-MIME receiver</ja:l>
347 <ja:l xml:lang="ja">8$B%S%C%HAw?.<T$+$i(B7$B%S%C%HHs(B MIME $B<u?.<T$X(B</ja:l>
348 </ja:pair>
349 <vspace blankLines="1" />
350 <ja:pair>
351 <ja:l xml:lang="en">
352 The receiver will receive bit-stripped mail which results in the
353 mis-interpretation of the data and the wrong character being
354 displayed or printed. Mail sent using languages where most
355 characters are in the US-ASCII subset of ISO 8859 may be somewhat
356 readable.
357 </ja:l>
358 <ja:l xml:lang="ja">
359 $B<u?.<T$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
360 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$^$;$s!#(B
361 </ja:l>
362 </ja:pair>
363 </t>
364
365 <t hangText="(3)" ja:anchor="s2.i3">
366 <ja:pair>
367 <ja:l xml:lang="en">8bit transparent sender to 8bit transparent receiver</ja:l>
368 <ja:l xml:lang="ja">8$B%S%C%HF)2aAw?.<T$+$i(B8$B%S%C%HF)2a<u?.<T$X(B</ja:l>
369 </ja:pair>
370 <vspace blankLines="1" />
371 <ja:pair>
372 <ja:l xml:lang="en">
373 Will work if an external agreement "out of band" to use a
374 particular character set without tagging exists between the sender
375 and the receiver.
376 </ja:l>
377 <ja:l xml:lang="ja">
378 $BFCDjJ8;z=89g$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$&!#(B
379 </ja:l>
380 </ja:pair>
381 </t>
382
383 <t hangText="(4)" ja:anchor="s2.i4">
384 <ja:pair>
385 <ja:l xml:lang="en">8bit transparent sender to MIME/ESMTP conformant receiver</ja:l>
386 <ja:l xml:lang="ja">8$B%S%C%HF)2aAw?.<T$+$i(B MIME/ESMTP $BE,9g<u?.<T$X(B</ja:l>
387 </ja:pair>
388 <vspace blankLines="1" />
389 <ja:pair>
390 <ja:l xml:lang="en">
391 Will work if a reasonable upgrade path is provided via gateways,
392 the indicated character set tag inserted by the gateway is correct
393 and the receiver supports the character set chosen by the sender.
394 This case is the focus of this memo.
395 </ja:l>
396 <ja:l xml:lang="ja">
397 $BJ,JL$"$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
398 </ja:l>
399 </ja:pair>
400 </t>
401
402 <t hangText="(5)" ja:anchor="s2.i5">
403 <ja:pair>
404 <ja:l xml:lang="en">MIME/ESMTP sender to non-MIME 7bit receiver</ja:l>
405 <ja:l xml:lang="ja">MIME/ESMTP $BAw?.<T$+$iHs(B MIME 7$B%S%C%H<u?.<T$X(B</ja:l>
406 </ja:pair>
407 <vspace blankLines="1" />
408 <ja:pair>
409 <ja:l xml:lang="en">
410 Because the ESMTP/MIME sender cannot know if the receiver will
411 understand 8bits, the sender will encode the text into base-64 or
412 quoted-printable which may be considered "garbled" by the
413 receiver. To provide a useful downgrade path the gateway must
414 have some knowledge about the capabilities of the receiver. When
415 the character set can be clearly identified, techniques like the
416 menmonic MNEM encoding described in RFC 1345 may be helpful in
417 this case.
418 </ja:l>
419 <ja:l xml:lang="ja">
420 ESMTP/MIME $BAw?.<T$O<u?.<T$,(B8$B%S%C%H$rM}2r$9$k$+$I$&$+CN$jF@$J$$$N$G!"Aw?.<T$OJ8$r(B
421 base-64 $B$+<u?.<T$K!VJ8;z2=$1$7$?!W$H;W$o$l$k$+$b$7$l$J$$(B
422 quoted-printable
423 $B$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$$$F$NCN<1$rM-$9$kI,MW$,$"$j$^$9!#J8;z=89g$,L@3N$K<1JL=PMh$k;~$O!"(B
424 <ja:link type="rfc" number="1345" /> $B$G@bL@$5$l$F$$$k5-K!(B MNEM
425 $BId9f2=$NMM$J<jK!$,$3$N>l9g$K$OM-MQ$+$b$7$l$^$;$s!#(B
426 </ja:l>
427 </ja:pair>
428 </t>
429
430 <t hangText="(6)" ja:anchor="s2.i6">
431 <ja:pair>
432 <ja:l xml:lang="en">MIME/ESMTP sender to MIME/ESMTP receiver</ja:l>
433 <ja:l xml:lang="ja">MIME/ESMTP $BAw?.<T$+$i(B MIME/ESMTP $B<u?.<T$X(B</ja:l>
434 </ja:pair>
435 <vspace blankLines="1" />
436 <ja:pair>
437 <ja:l xml:lang="en">
438 Interoperability will be attained provided the receiver supports
439 the character set chosen by the sender.
440 </ja:l>
441 <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$^$9!#(B</ja:l>
442 </ja:pair>
443 </t>
444 </list>
445 </t>
446 </section>
447
448 <section title="Upgrade Path from 8bit Transparent to ESMTP/MIME"
449 ja:title-ja="8$B%S%C%HF)2a$+$i(B ESMTP/MIME $B$X$N(B&ja.upgrade;$B7PO)(B"><!-- 3. -->
450
451 <t>
452 <ja:pair>
453 <ja:l xml:lang="en">
454 A gateway which has been upgraded to support Extended SMTP may
455 upgrade an 8bit message received to MIME. This is consistent with
456 the requirement that all 8bit mail sent by ESMTP be encoded in MIME.
457 The upgrade should be done using the best available information.
458 </ja:l>
459 <ja:l xml:lang="ja">
460 $B3HD%(B SMTP
461 $B$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
462 MIME $B$K(B&ja.upgrade;$B$7$F9=$$$^$;$s!#$3$l$O(B ESMTP
463 $B$GAw?.$5$l$k(B8$B%S%C%H!&%a%$%k$OA4$F(B
464 MIME $B$GId9f2=$5$l$F$$$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
465 </ja:l>
466 </ja:pair>
467 </t>
468
469 <t>
470 <ja:pair>
471 <ja:l xml:lang="en">
472 A site may "upgrade" to MIME en-masse by implementing MIME conversion
473 for all messages leaving the site. For text messages, the body can
474 be converted by adding a MIME-version header and a Content-Type:
475 Text/Plain with the character set in use in the site, provided the
476 site uses a single character set.
477 </ja:l>
478 <ja:l xml:lang="ja">
479 $B%5%$%H$O!"%5%$%H$rN%$l$kA4$F$N%a%C%;!<%8$r!"(B
480 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
481 MIME-version $BF,$H(B Content-Type: Text/Plain
482 $B$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
483 </ja:l>
484 </ja:pair>
485 </t>
486
487 <t>
488 <ja:pair>
489 <ja:l xml:lang="en">
490 An appropriate Content-Transfer-Encoding header line must be added to
491 indicate any encoding that may be necessary.
492 </ja:l>
493 <ja:l xml:lang="ja">
494 $BE,@Z$J(B Content-Transfer-Encoding
495 $BF,9T$r!"I,MW$+$b$7$l$J$$Id9f2=$r<($9$N$K2C$($J$1$l$P$J$j$^$;$s!#(B
496 </ja:l>
497 </ja:pair>
498 </t>
499
500 <!--
501 Example:
502 --><ja:example xml:space="preserve">
503 MIME-Version: 1.0
504 Content-Type: Text/Plain; Charset = ISO-8859-1
505 Content-Transfer-Encoding: 8bit
506 </ja:example>
507
508 <t>
509 <ja:pair>
510 <ja:l xml:lang="en">
511 If no information about the character set in use is available, the
512 gateway should upgrade the content by using the character set
513 "unknown-8bit". The unknown-8bit value of the charset parameter
514 indicates only that no reliable information about the character
515 set(s) used in the message was available.
516 </ja:l>
517 <ja:l xml:lang="ja">
518 $B;HMQ$5$l$F$$$kJ8;z=89g$K$D$$$F$N>pJs$,L5$$>l9g$O!"(B&ja.mail.gateway;$B$OFbMF$rJ8;z=89g(B
519 "unknown-8bit" $B$r;H$C$F(B&ja.upgrade;$B$9$k$Y$-$G$9!#(B charset
520 $B%Q%i%a!<%?!<$N(B unknown-8bit
521 $BCM$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
522 </ja:l>
523 </ja:pair>
524 </t>
525
526 <t>
527 <ja:pair>
528 <ja:l xml:lang="en">
529 If a message body has been upgraded to MIME, the RFC 822 headers
530 containing non US-ASCII characters must be upgraded to conform with
531 the header encoding rules of RFC1342. A gateway should recode all
532 unstructered header fields as well as RFC 822 "comment"s and
533 "phrase"s according to the rules of RFC 1342. There is no equivalent
534 in RFC 1342 to the "8bit" Content-Transfer-Encoding value for message
535 bodies so all 8bit header text must be transformed according to
536 either the "B" or the "Q" encoding method. For ISO 8859 character
537 sets, the "Q" encoding will generally result in somewhat readable
538 headers.
539 </ja:l>
540 <ja:l xml:lang="ja">
541 $B%a%C%;!<%8(B&ja.body;$B$,(B MIME $B$K(B&ja.upgrade;$B$5$l$k>l9g!"Hs(B US-ASCII
542 $BJ8;z$r4^$`(B <ja:link type="rfc" number="822" /> $BF,$O(B
543 RFC 1342
544 $B$NF,Id9f2=5,B'$KE,9g$9$k$h$&(B&ja.upgrade;$B$7$J$1$l$P$J$j$^$;$s!#(B&ja.mail.gateway;$B$OA4$F$NHs9=B$2=F,NN0h$H(B
545 RFC 822 "comment" $B$H(B "phrase" $B$r(B RFC 1342
546 $B$N5,B'$K=>$$:FId9f2=$9$k$Y$-$G$9!#%a%C%;!<%8(B&ja.body;$B$N(B "8bit"
547 $BFbMFE>AwId9f2=CM$KAjEv$9$k$b$N$O(B RFC 1342
548 $B$K$OL5$$$N$G!"A4$F$N(B8$B%S%C%HF,J8$O(B "B" $BId9f2=J}<0$^$?$O(B "Q"
549 $BId9f2=J}<0$GId9f2=$7$J$1$l$P$J$j$^$;$s!#(B ISO 8859 $BJ8;z=89g$K$O!"(B
550 "Q" $BId9f2=$r;H$&$H!"DL>o$d$d2DFI$JF,$H$J$j$^$9!#(B
551 </ja:l>
552 </ja:pair>
553 </t>
554
555 <figure>
556 <preamble>
557 <ja:pair>
558 <ja:l xml:lang="en">
559 Trace information should be added to the document with a convert
560 clause: "rfc822-to-8bit", "rfc822-to-base-64" or "rfc822-to-quoted-
561 printable" e.g.,
562 </ja:l>
563 <ja:l xml:lang="ja">
564 $BDI@W>pJs$r<!$NNc$N$h$&$KJQ49(B (convert) $B>r9`(B "rfc822-to-8bit",
565 "rfc822-to-base-64", "rfc822-to-quoted-printable"
566 $B$D$-$GJ8=q$KDI2C$9$k$Y$-$G$9!#(B
567 </ja:l>
568 </ja:pair>
569 </preamble>
570
571 <artwork xml:space="preserve">
572 Received: from dbc.mtview.ca.us by dbc.mtview.ca.us
573 convert rfc822-to-8bit; Tue, 01 Sep 1992 01:18:00 -0700
574 </artwork>
575 </figure>
576 </section>
577
578 <section title="Appendix $B!=(B The &quot;unknown-8bit&quot; Character Set"
579 ja:title-ja="$BImB0=q(B $B!=(B &quot;unknown-8bit&quot; $BJ8;z=89g(B"
580 myns:unnumbered="yes">
581
582 <t>
583 <ja:pair>
584 <ja:l xml:lang="en">
585 This section defines a "charset" parameter, for use in a MIME
586 Content-Type field.
587 </ja:l>
588 <ja:l xml:lang="ja">
589 $B$3$N@a$G$O(B MIME Content-Type $BNN0h$G;H$&(B "charset"
590 $B%Q%i%a!<%?!<$rDj5A$7$^$9!#(B
591 </ja:l>
592 </ja:pair>
593 </t>
594
595 <t>
596 <ja:pair>
597 <ja:l xml:lang="en">
598 A special purpose character set called "unknown-8bit" is defined to
599 be an unknown 8bit character set, encoded into a sequence of octets.
600 It can be used as a label for any character set from any language,
601 using any encoding. It must not be further defined.
602 </ja:l>
603 <ja:l xml:lang="ja">
604 "unknown-8bit"
605 $B$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$$$+$J$kJ8;z=89g$K$b;%$H$7$F;H$&$3$H$,=PMh$^$9!#$3$l0J>e$ODj5A$7$^$;$s!#(B
606 </ja:l>
607 </ja:pair>
608 </t>
609
610 <t>
611 <ja:pair>
612 <ja:l xml:lang="en">
613 The use of this token in a "charset=" field of a message indicates
614 that nothing is known about the character set used. This marker is
615 intended for use by non-MIME to MIME gateways; specifically in those
616 which translate from SMTP to 8bit ESMTP/MIME.
617 </ja:l>
618 <ja:l xml:lang="ja">
619 $B$3$N;z6g$r%a%C%;!<%8$N(B "charset="
620 $BNN0h$G;H$&$3$H$G!";H$o$l$F$$$kJ8;z=89g$K$D$$$FA4$/$b$C$FITL@$G$"$k$3$H$r<($7$^$9!#$3$N0u$OHs(B
621 MIME $B$+$i(B MIME $B$X$N(B&ja.mail.gateway;$B!"6qBNE*$K$O(B SMTP
622 $B$+$i(B8$B%S%C%H(B ESMTP/MIME
623 $B$KJQ49$9$k(B&ja.mail.gateway;$B$G;H$&$3$H$r0U?^$7$F$$$^$9!#(B
624 </ja:l>
625 </ja:pair>
626 </t>
627
628 <t>
629 <ja:pair>
630 <ja:l xml:lang="en">
631 This character set is not intended to be used by mail composers.
632 It is assumed that the mail composer knows the character set in
633 use and will mark it with a character set value as specified in
634 <xref target="refs.RFC1341" />, as amended by current Assigned
635 Numbers documents <xref target="refs.STD2" />.
636 </ja:l>
637 <ja:l xml:lang="ja">
638 $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
639 <xref target="refs.RFC1341" /> $B$G5,Dj$5$l$F8=9T$N3dEvHV9fJ8=q(B
640 <xref target="refs.STD2" />
641 $B$G2~D{$5$l$?J8;z=89gCM$G0u$r$D$1$k$HA[Dj$7$F$$$^$9!#(B
642 </ja:l>
643 </ja:pair>
644 </t>
645
646 <t>
647 <ja:pair>
648 <ja:l xml:lang="en">
649 The use of the "unknown-8bit" label is intended only by mail gateway
650 agents which cannot determine via out-of-band information the
651 intended character set.
652 </ja:l>
653 <ja:l xml:lang="ja">
654 "unknown-8bit"
655 $B;%$N;HMQ$O!"(B&ja.outofband;$B>pJs$K$h$j0U?^$5$l$?J8;z=89g$r7hDj=PMh$J$$%a%$%k(B&ja.mail.gateway;&ja.agent;$B$K$h$j$N$_;H$o$l$k$3$H$rA[Dj$7$F$$$^$9!#(B
656 </ja:l>
657 </ja:pair>
658 </t>
659
660 <t>
661 <ja:pair>
662 <ja:l xml:lang="en">
663 The interpretation of the "unknown-8bit" is up to the mail reader.
664 It is assumed that in many cases the human user will be able to
665 interpret the information and choose an appropriate character set or
666 pre-processor.
667 </ja:l>
668 <ja:l xml:lang="ja">
669 "unknown-8bit"
670 $B$N2r<a$O(B&ja.mail.mail-reader;$B$K0Q$M$i$l$^$9!#B?$/$N>l9g$G$O?M4VMxMQ<T$,>pJs$r2r<a$7$FE,@Z$JJ8;z=89g$"$k$$$OA0=hM}4o$rA*Br$G$-$k$H;W$o$l$^$9!#(B
671 </ja:l>
672 </ja:pair>
673 </t>
674
675 </section>
676
677 <section title="Acknowledgements" myns:unnumbered="yes">
678 <t>
679 <ja:pair>
680 <ja:l xml:lang="en">
681 This document originated as a hallway conversation between
682 Ned Freed, Neil Katin, and the author. Substantive input
683 was received from Jonathan Laventhol, Craig Everhart,
684 Olle Jarnefors, and Olafur Gudmundsson. The document was
685 refined with the input of many participants in the IETF SMTP
686 Extensions Working Group.
687 </ja:l>
688 <ja:l xml:lang="ja">
689 $B$3$NJ8=q$O(B Ned Freed, Neil Katin $B$HCx<T$N0f8MC<2q5D$+$i@8$^$l$^$7$?!#(B
690 Jonathan Laventhol, Craig Everhart,
691 Olle Jarnefors, Olafur Gudmundsson
692 $B$,:2$r?a$-9~$s$G$/$l$^$7$?!#$3$NJ8=q$O(B
693 IETF SMTP $B3HD%:n6HIt2q$N;22C<T$N0U8+$K$h$j@:O#$5$l$^$7$?!#(B
694 </ja:l>
695 </ja:pair>
696 </t>
697 </section>
698
699 <ja:insert section="references" />
700
701
702 <section title="Security Considerations" myns:unnumbered="yes">
703 <t>Security issues are not discussed in this memo.</t>
704 </section>
705
706 </middle>
707 <back>
708 <references>
709 <reference anchor="refs.RFC1341"><!-- [1] -->
710 <front><title>Multipurpose Internet Mail Extensions</title>
711 <ja:title xml:lang="ja">$BB?L\E*(B Internet $B%a%$%k3HD%(B</ja:title>
712 <author initials="N." surname="Borenstein">
713 <organization>Bellcore</organization>
714 </author>
715 <author initials="N." surname="Freed">
716 <organization>Innosoft</organization>
717 </author>
718 <date month="June" year="1992" />
719 </front>
720 <seriesInfo name="RFC" value="1341" />
721 </reference>
722 <reference anchor="refs.RFC1342"><!-- [2] -->
723 <front><title>Representation of Non-ASCII Text in
724 Internet Message Headers</title>
725 <ja:title xml:lang="ja">$BHs(B ASCII $BJ8$N(B Internet
726 $B%a%C%;!<%8F,$K$*$1$kI=8=(B</ja:title>
727 <author initials="K." surname="Moore">
728 <organization>University of Tennessee</organization>
729 </author>
730 <date month="June" year="1992" />
731 </front>
732 <seriesInfo name="RFC" value="1342" />
733 </reference>
734 <reference anchor="refs.RFC1425"><!-- [3] -->
735 <front><title>SMTP Service Extensions</title>
736 <ja:title xml:lang="ja">SMTP $B%5!<%S%93HD%(B</ja:title>
737 <author initials="J." surname="Klensin" ja:text="Klensin, J., WG Chair">
738 <organization>United Nations University</organization>
739 </author>
740 <author initials="N." surname="Freed" ja:text="Freed, N., Editor">
741 <organization>Innosoft International, Inc.</organization>
742 </author>
743 <author initials="M." surname="Rose">
744 <organization>Dover Beach Consulting, Inc.</organization>
745 </author>
746 <author initials="E." surname="Stefferud">
747 <organization>Network Management Associates, Inc.</organization>
748 </author>
749 <author initials="D." surname="Crocker">
750 <organization>The Branch Office</organization>
751 </author>
752 <date month="February" year="1993" />
753 </front>
754 <seriesInfo name="RFC" value="1425" />
755 </reference>
756 <reference anchor="refs.RFC1426"><!-- [4] -->
757 <front><title>SMTP Service Extensions for 8bit
758 MIMEtransport</title>
759 <ja:title xml:lang="ja">8$B%S%C%H(B MIME $BE>AwMQ(B
760 SMTP $B%5!<%S%93HD%(B</ja:title>
761 <author initials="J." surname="Klensin" ja:text="Klensin, J., WG Chair">
762 <organization>United Nations University</organization>
763 </author>
764 <author initials="N." surname="Freed" ja:text="Freed, N., Editor">
765 <organization>Innosoft International, Inc.</organization>
766 </author>
767 <author initials="M." surname="Rose">
768 <organization>Dover Beach Consulting, Inc.</organization>
769 </author>
770 <author initials="E." surname="Stefferud">
771 <organization>Network Management Associates, Inc.</organization>
772 </author>
773 <author initials="D." surname="Crocker">
774 <organization>The Branch Office</organization>
775 </author>
776 <date month="February" year="1993" />
777 </front>
778 <seriesInfo name="RFC" value="1426" />
779 </reference>
780 <reference anchor="refs.ASCII"><!-- [5] -->
781 <front><title>Coded Character Set$B!=!=(B7-Bit American Standard Code
782 for Information Interchange</title>
783 <ja:title xml:lang="ja">$BId9f2=J8;z=89g!=!=(B7$B%S%C%H$N>pJs8r49MQ0!JFMx2CI8=`Id9f(B</ja:title>
784 </front>
785 <seriesInfo name="ANSI" value="X3.4-1986" />
786 </reference>
787 <reference anchor="refs.STD2"><!-- [6] -->
788 <front><title>Assigned Numbers</title>
789 <ja:title xml:lang="ja">$B3dEvHV9f(B</ja:title>
790 <author initials="J." surname="Reynolds">
791 <organization>USC/Information Sciences Institute</organization>
792 </author>
793 <author initials="J." surname="Postel">
794 <organization>USC/Information Sciences Institute</organization>
795 </author>
796 <date month="July" year="1992" />
797 </front>
798 <seriesInfo name="STD" value="2" />
799 <seriesInfo name="RFC" value="1340" />
800 </reference>
801 </references>
802 </back>
803 </rfc>

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