intro.ps

早期freebsd实现

2.922 F .422(werful enough to)-.25 F(re)112 319.8 Q 1.357(write addresses in t\
he message header to conform to the standards of a number of)-.25 F 1.15
(common tar)112 331.8 R 1.15(get netw)-.18 F 1.15
(orks, including old \(NCP/RFC733\) Arpanet, ne)-.1 F 3.65(w\()-.25 G
(TCP/RFC822\))405.65 331.8 Q 1.119(Arpanet, UUCP)112 343.8 R 3.619(,a)-1.11 G
1.119(nd Phonenet.)186.448 343.8 R 1.119(Sendmail also implements an SMTP serv)
6.119 F(er)-.15 E 3.619(,m)-.4 G(essage)437.9 343.8 Q(queueing, and aliasing.)
112 355.8 Q F2(Sendmail)97 400.2 Q F1 .501(implements a general internetw)3 F
.501(ork mail routing f)-.1 F(acility)-.1 E 3.001(,f)-.65 G .501
(eaturing aliasing and forw)369.847 400.2 R(arding,)-.1 E
(automatic routing to netw)72 412.2 Q(ork g)-.1 E(ate)-.05 E -.1(wa)-.25 G
(ys, and \215e).1 E(xible con\214guration.)-.15 E .624(In a simple netw)97
428.4 R .624(ork, each node has an address, and resources can be identi\214ed \
with a host-resource)-.1 F .374(pair; in particular)72 440.4 R 2.874(,t)-.4 G
.374(he mail system can refer to users using a host-username pair)149.932 440.4
R 5.374(.H)-.55 G .375(ost names and numbers)409.276 440.4 R(ha)72 452.4 Q .3
-.15(ve t)-.2 H 2.5(ob).15 G 2.5(ea)108.31 452.4 S
(dministered by a central authority)119.69 452.4 Q 2.5(,b)-.65 G
(ut usernames can be assigned locally to each host.)263.82 452.4 Q .649
(In an internet, multiple netw)97 468.6 R .649(orks with dif)-.1 F .649
(ferent characterstics and managements must communicate.)-.25 F .389
(In particular)72 480.6 R 2.889(,t)-.4 G .389
(he syntax and semantics of resource identi\214cation change.)129.308 480.6 R
.39(Certain special cases can be han-)5.389 F 1.033(dled tri)72 492.6 R 1.033
(vially by)-.25 F F2 1.033(ad hoc)3.533 F F1 1.032(techniques, such as pro)
3.533 F 1.032(viding netw)-.15 F 1.032
(ork names that appear local to hosts on other)-.1 F(netw)72 504.6 Q 1.454
(orks, as with the Ethernet at Xerox P)-.1 F 3.955(ARC. Ho)-.92 F(we)-.25 E
-.15(ve)-.25 G 4.755 -.4(r, t).15 H 1.455(he general case is e).4 F 1.455
(xtremely comple)-.15 F 3.955(x. F)-.15 F(or)-.15 E -.15(ex)72 516.6 S .192
(ample, some netw).15 F .192(orks require point-to-point routing, which simpli\
\214es the database update problem since)-.1 F .618(only adjacent hosts must b\
e entered into the system tables, while others use end-to-end addressing.)72
528.6 R(Some)5.618 E(netw)72 540.6 Q .123(orks use a left-associati)-.1 F .423
-.15(ve s)-.25 H .123(yntax and others use a right-associati).15 F .423 -.15
(ve s)-.25 H .123(yntax, causing ambiguity in mix).15 F(ed)-.15 E(addresses.)72
552.6 Q .678(Internet standards seek to eliminate these problems.)97 568.8 R
(Initially)5.678 E 3.178(,t)-.65 G .679(hese proposed e)353.134 568.8 R .679
(xpanding the address)-.15 F .65(pairs to address triples, consisting of {netw)
72 580.8 R .649(ork, host, resource} triples.)-.1 F(Netw)5.649 E .649
(ork numbers must be uni)-.1 F -.15(ve)-.25 G -.2(r-).15 G 1.452
(sally agreed upon, and hosts can be assigned locally on each netw)72 592.8 R
3.952(ork. The)-.1 F(user)3.952 E(-le)-.2 E -.15(ve)-.25 G 3.952(lp).15 G 1.452
(resentation w)440.718 592.8 R(as)-.1 E 2.352(quickly e)72 604.8 R 2.352(xpand\
ed to address domains, comprised of a local resource identi\214cation and a hi\
erarchical)-.15 F .256(domain speci\214cation with a common static root.)72
616.8 R .257(The domain technique separates the issue of ph)5.257 F .257
(ysical v)-.05 F(er)-.15 E(-)-.2 E .807(sus logical addressing.)72 628.8 R -.15
(Fo)5.807 G 3.307(re).15 G .807
(xample, an address of the form \[e-mail])191.028 628.8 R(ele)-.1 E
-.65(y.)-.15 G .807(arpa\232 describes only the).65 F(logical or)72 640.8 Q
-.05(ga)-.18 G(nization of the address space.).05 E F2(Sendmail)97 657 Q F1
.493(is intended to help bridge the g)2.992 F .493(ap between the totally)-.05
F F2 .493(ad hoc)2.993 F F1 -.1(wo)2.993 G .493(rld of netw).1 F .493
(orks that kno)-.1 F(w)-.25 E .855
(nothing of each other and the clean, tightly-coupled w)72 669 R .854
(orld of unique netw)-.1 F .854(ork numbers.)-.1 F .854(It can accept old)5.854
F .32 LW 76 678.6 72 678.6 DL 80 678.6 76 678.6 DL 84 678.6 80 678.6 DL 88
678.6 84 678.6 DL 92 678.6 88 678.6 DL 96 678.6 92 678.6 DL 100 678.6 96 678.6
DL 104 678.6 100 678.6 DL 108 678.6 104 678.6 DL 112 678.6 108 678.6 DL 116
678.6 112 678.6 DL 120 678.6 116 678.6 DL 124 678.6 120 678.6 DL 128 678.6 124
678.6 DL 132 678.6 128 678.6 DL 136 678.6 132 678.6 DL 140 678.6 136 678.6 DL
144 678.6 140 678.6 DL 148 678.6 144 678.6 DL 152 678.6 148 678.6 DL 156 678.6
152 678.6 DL 160 678.6 156 678.6 DL 164 678.6 160 678.6 DL 168 678.6 164 678.6
DL 172 678.6 168 678.6 DL 176 678.6 172 678.6 DL 180 678.6 176 678.6 DL 184
678.6 180 678.6 DL 188 678.6 184 678.6 DL 192 678.6 188 678.6 DL 196 678.6 192
678.6 DL 200 678.6 196 678.6 DL 204 678.6 200 678.6 DL 208 678.6 204 678.6 DL
212 678.6 208 678.6 DL 216 678.6 212 678.6 DL/F3 8/Times-Roman@0 SF .557
(*A considerable part of this w)93.6 690.6 R .557(ork w)-.08 F .557
(as done while under the emplo)-.08 F 2.557(yo)-.08 G 2.556(ft)323.116 690.6 S
.556(he INGRES Project at the Uni)330.56 690.6 R -.12(ve)-.2 G .556
(rsity of California at).12 F(Berk)72 700.2 Q(ele)-.08 E 2(ya)-.12 G
(nd at Britton Lee.)106.232 700.2 Q/F4 10/Times-Bold@0 SF
(SENDMAIL \212 An Inter)72 756 Q(netw)-.15 E(ork Mail Router)-.1 E(SMM:9-1)
462.9 756 Q EP
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/F0 10/Times-Bold@0 SF 192.28(SMM:9-2 SENDMAIL)72 60 R 2.5<8a41>2.5 G 2.5(nI)
383.99 60 S(nter)395.94 60 Q(netw)-.15 E(ork Mail Router)-.1 E/F1 10
/Times-Roman@0 SF .632(arbitrary address syntax)72 96 R .633(es, resolving amb\
iguities using heuristics speci\214ed by the system administrator)-.15 F 3.133
(,a)-.4 G(s)500.11 96 Q .348(well as domain-based addressing.)72 108 R .347
(It helps guide the con)5.347 F -.15(ve)-.4 G .347
(rsion of message formats between disparate net-).15 F -.1(wo)72 120 S 3.394
(rks. In).1 F(short,)3.394 E/F2 10/Times-Italic@0 SF(sendmail)3.394 E F1 .894
(is designed to assist a graceful transition to consistent internetw)3.394 F
.895(ork addressing)-.1 F(schemes.)72 132 Q .153
(Section 1 discusses the design goals for)97 160.2 R F2(sendmail)2.653 E F1
5.153(.S)C .152(ection 2 gi)308.214 160.2 R -.15(ve)-.25 G 2.652(sa).15 G 2.652
(no)370.76 160.2 S -.15(ve)383.262 160.2 S(rvie).15 E 2.652(wo)-.25 G 2.652(ft)
422.724 160.2 S .152(he basic functions)431.486 160.2 R .644(of the system.)72
172.2 R .644(In section 3, details of usage are discussed.)5.644 F .644
(Section 4 compares)5.644 F F2(sendmail)3.144 E F1 .645(to other internet)3.144
F(mail routers, and an e)72 184.2 Q -.25(va)-.25 G(luation of).25 E F2
(sendmail)2.5 E F1(is gi)2.5 E -.15(ve)-.25 G 2.5(ni).15 G 2.5(ns)283.3 184.2 S
(ection 5, including future plans.)294.69 184.2 Q F0 2.5(1. DESIGN)72 208.2 R
(GO)2.5 E(ALS)-.4 E F1(Design goals for)112 224.4 Q F2(sendmail)2.5 E F1
(include:)2.5 E 12.5(\(1\) Compatibility)92 240.6 R 1.363(with the e)3.864 F
1.363(xisting mail programs, including Bell v)-.15 F 1.363
(ersion 6 mail, Bell v)-.15 F 1.363(ersion 7)-.15 F 1.202(mail [UNIX83], Berk)
118.66 252.6 R(ele)-.1 E(y)-.15 E F2(Mail)3.702 E F1 1.202
([Shoens79], BerkNet mail [Schmidt79], and hopefully UUCP)3.702 F(mail [No)
118.66 264.6 Q(witz78a, No)-.25 E 2.5(witz78b]. ARP)-.25 F(ANET mail [Crock)
-.92 E(er77a, Postel77] w)-.1 E(as also required.)-.1 E 12.5(\(2\) Reliability)
92 280.8 R 4.003(,i)-.65 G 4.003(nt)169.523 280.8 S 1.502
(he sense of guaranteeing that e)181.306 280.8 R -.15(ve)-.25 G 1.502
(ry message is correctly deli).15 F -.15(ve)-.25 G 1.502(red or at least).15 F
.368
(brought to the attention of a human for correct disposal; no message should e)
118.66 292.8 R -.15(ve)-.25 G 2.868(rb).15 G 2.868(ec)452.252 292.8 S
(ompletely)464 292.8 Q 2.541(lost. This)118.66 304.8 R .041(goal w)2.541 F .041
(as considered essential because of the emphasis on mail in our en)-.1 F 2.54
(vironment. It)-.4 F 1.754
(has turned out to be one of the hardest goals to satisfy)118.66 316.8 R 4.255
(,e)-.65 G 1.755(specially in the f)363.75 316.8 R 1.755(ace of the man)-.1 F
(y)-.15 E .978(anomalous message formats produced by v)118.66 328.8 R .977
(arious ARP)-.25 F .977(ANET sites.)-.92 F -.15(Fo)5.977 G 3.477(re).15 G .977
(xample, certain sites)420.116 328.8 R .069
(generate improperly formated addresses, occasionally causing error)118.66
340.8 R .069(-message loops.)-.2 F .069(Some hosts)5.069 F .063(use blanks in \
names, causing problems with UNIX mail programs that assume that an address is)
118.66 352.8 R .111(one w)118.66 364.8 R 2.611(ord. The)-.1 F .111
(semantics of some \214elds are interpreted slightly dif)2.611 F .112
(ferently by dif)-.25 F .112(ferent sites.)-.25 F(In)5.112 E(summary)118.66
376.8 Q 3.023(,t)-.65 G .523(he obscure features of the ARP)163.533 376.8 R
.523(ANET mail protocol really)-.92 F F2(ar)3.023 E(e)-.37 E F1 .522
(used and are dif)3.023 F(\214cult)-.25 E(to support, b)118.66 388.8 Q
(ut must be supported.)-.2 E 12.5(\(3\) Existing)92 405 R(softw)2.938 E .438
(are to do actual deli)-.1 F -.15(ve)-.25 G .439(ry should be used whene).15 F
-.15(ve)-.25 G 2.939(rp).15 G 2.939(ossible. This)387.654 405 R .439(goal deri)
2.939 F -.15(ve)-.25 G 2.939(sa).15 G(s)500.11 405 Q
(much from political and practical considerations as technical.)118.66 417 Q
12.5(\(4\) Easy)92 433.2 R -.15(ex)2.899 G .399(pansion to f).15 F .399
(airly comple)-.1 F 2.898(xe)-.15 G -.4(nv)261.064 433.2 S .398
(ironments, including multiple connections to a single net-).4 F -.1(wo)118.66
445.2 S .115
(rk type \(such as with multiple UUCP or Ether nets [Metcalfe76]\).).1 F .115
(This goal requires consid-)5.115 F .587(eration of the contents of an address\
 as well as its syntax in order to determine which g)118.66 457.2 R(ate)-.05 E
-.1(wa)-.25 G(y).1 E 1.018(to use.)118.66 469.2 R -.15(Fo)6.018 G 3.518(re).15
G 1.018(xample, the ARP)173.354 469.2 R 1.019
(ANET is bringing up the TCP protocol to replace the old NCP)-.92 F 4.791
(protocol. No)118.66 481.2 R 2.291(host at Berk)4.791 F(ele)-.1 E 4.791(yr)-.15
G 2.291(uns both TCP and NCP)256.235 481.2 R 4.791(,s)-1.11 G 4.79(oi)369.37
481.2 S 4.79(ti)381.94 481.2 S 4.79(sn)392.29 481.2 S 2.29
(ecessary to look at the)405.97 481.2 R(ARP)118.66 493.2 Q .016
(ANET host name to determine whether to route mail to an NCP g)-.92 F(ate)-.05
E -.1(wa)-.25 G 2.517(yo).1 G 2.517(raT)435.569 493.2 S .017(CP g)454.483 493.2
R(ate)-.05 E -.1(wa)-.25 G -.65(y.).1 G 12.5(\(5\) Con\214guration)92 509.4 R
.145(should not be compiled into the code.)2.645 F 2.645(As)5.145 G .145
(ingle compiled program should be able)346.905 509.4 R .91(to run as is at an)
118.66 521.4 R 3.41(ys)-.15 G .91
(ite \(barring such basic changes as the CPU type or the operating system\).)
200.63 521.4 R 2.61 -.8(We h)118.66 533.4 T -2.25 -.2(av e).8 H 1.009
(found this seemingly unimportant goal to be critical in real life.)3.71 F
1.009(Besides the simple)6.009 F .66(problems that occur when an)118.66 545.4 R
3.16(yp)-.15 G .66(rogram gets recompiled in a dif)249.84 545.4 R .66
(ferent en)-.25 F .66(vironment, man)-.4 F 3.16(ys)-.15 G(ites)490.11 545.4 Q
(lik)118.66 557.4 Q 2.5(et)-.1 G 2.5<6f99>138.84 557.4 S(\214ddle\232 with an)
150.78 557.4 Q(ything that the)-.15 E 2.5(yw)-.15 G(ill be recompiling an)
282.42 557.4 Q(yw)-.15 E(ay)-.1 E(.)-.65 E(\(6\))92 573.6 Q F2(Sendmail)118.66
573.6 Q F1 .184(must be able to let v)2.684 F .184
(arious groups maintain their o)-.25 F .184(wn mailing lists, and let indi)-.25
F(viduals)-.25 E(specify their o)118.66 585.6 Q(wn forw)-.25 E
(arding, without modifying the system alias \214le.)-.1 E 12.5(\(7\) Each)92
601.8 R .313(user should be able to specify which mailer to e)2.813 F -.15(xe)
-.15 G .313(cute to process mail being deli).15 F -.15(ve)-.25 G .314(red for)
.15 F 3.098(him. This)118.66 613.8 R .598(feature allo)3.098 F .598
(ws users who are using specialized mailers that use a dif)-.25 F .598
(ferent format to)-.25 F -.2(bu)118.66 625.8 S .25(ild their en).2 F .25
(vironment without changing the system, and f)-.4 F .25
(acilitates specialized functions \(such)-.1 F(as returning an \231I am on v)
118.66 637.8 Q(acation\232 message\).)-.25 E 12.5(\(8\) Netw)92 654 R 1.553
(ork traf)-.1 F 1.552(\214c should be minimized by batching addresses to a sin\
gle host where possible,)-.25 F(without assistance from the user)118.66 666 Q
(.)-.55 E .374(These goals moti)112 682.2 R -.25(va)-.25 G .374
(ted the architecture illustrated in \214gure 1.).25 F .375
(The user interacts with a mail gen-)5.375 F .491(erating and sending program.)
87 694.2 R .491(When the mail is created, the generator calls)5.491 F F2
(sendmail)2.99 E F1 2.99(,w)C .49(hich routes the)444.14 694.2 R .84
(message to the correct mailer\(s\).)87 706.2 R .841
(Since some of the senders may be netw)5.84 F .841(ork serv)-.1 F .841
(ers and some of the)-.15 F(mailers may be netw)87 718.2 Q(ork clients,)-.1 E
F2(sendmail)2.5 E F1(may be used as an internet mail g)2.5 E(ate)-.05 E -.1(wa)
-.25 G -.65(y.).1 G EP
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/F0 10/Times-Bold@0 SF(SENDMAIL \212 An Inter)72 60 Q(netw)-.15 E
(ork Mail Router)-.1 E(SMM:9-3)462.9 60 Q .4 LW 77 108 72 108 DL 79 108 74 108
DL 84 108 79 108 DL 89 108 84 108 DL 94 108 89 108 DL 99 108 94 108 DL 104 108
99 108 DL 109 108 104 108 DL 114 108 109 108 DL 119 108 114 108 DL 124 108 119
108 DL 129 108 124 108 DL 134 108 129 108 DL 139 108 134 108 DL 144 108 139 108
DL 149 108 144 108 DL 154 108 149 108 DL 159 108 154 108 DL 164 108 159 108 DL
169 108 164 108 DL 174 108 169 108 DL 179 108 174 108 DL 184 108 179 108 DL 189
108 184 108 DL 194 108 189 108 DL 199 108 194 108 DL 204 108 199 108 DL 209 108
204 108 DL 214 108 209 108 DL 219 108 214 108 DL 224 108 219 108 DL 229 108 224
108 DL 234 108 229 108 DL 239 108 234 108 DL 244 108 239 108 DL 249 108 244 108
DL 254 108 249 108 DL 259 108 254 108 DL 264 108 259 108 DL 269 108 264 108 DL
274 108 269 108 DL 279 108 274 108 DL 284 108 279 108 DL 289 108 284 108 DL 294
108 289 108 DL 299 108 294 108 DL 304 108 299 108 DL 309 108 304 108 DL 314 108
309 108 DL 319 108 314 108 DL 324 108 319 108 DL 329 108 324 108 DL 334 108 329
108 DL 339 108 334 108 DL 344 108 339 108 DL 349 108 344 108 DL 354 108 349 108
DL 359 108 354 108 DL 364 108 359 108 DL 369 108 364 108 DL 374 108 369 108 DL
379 108 374 108 DL 384 108 379 108 DL 389 108 384 108 DL 394 108 389 108 DL 399
108 394 108 DL 404 108 399 108 DL 409 108 404 108 DL 414 108 409 108 DL 419 108
414 108 DL 424 108 419 108 DL 429 108 424 108 DL 434 108 429 108 DL 439 108 434
108 DL 444 108 439 108 DL 449 108 444 108 DL 454 108 449 108 DL 459 108 454 108
DL 464 108 459 108 DL 469 108 464 108 DL 474 108 469 108 DL 479 108 474 108 DL
484 108 479 108 DL 489 108 484 108 DL 494 108 489 108 DL 499 108 494 108 DL 504
108 499 108 DL/F1 10/Times-Roman@0 SF(sender1)164.45 155.6 Q 144 135.6 144