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7 Network Working Group M. Rose
8 Request for Comments: 1081 TWG
9 November 1988
11 Post Office Protocol - Version 3
14 Status of this Memo
16 This memo suggests a simple method for workstations to dynamically
17 access mail from a mailbox server. This RFC specifies a proposed
18 protocol for the Internet community, and requests discussion and
19 suggestions for improvements. Distribution of this memo is
20 unlimited.
22 This memo is based on RFC 918 (since revised as RFC 937). Although
23 similar in form to the original Post Office Protocol (POP) proposed
24 for the Internet community, the protocol discussed in this memo is
25 similar in spirit to the ideas investigated by the MZnet project at
26 the University of California, Irvine.
28 Further, substantial work was done on examining POP in a PC-based
29 environment. This work, which resulted in additional functionality
30 in this protocol, was performed by the ACIS Networking Systems Group
31 at Stanford University. The author gratefully acknowledges their
32 interest.
34 Introduction
36 On certain types of smaller nodes in the Internet it is often
37 impractical to maintain a message transport system (MTS). For
38 example, a workstation may not have sufficient resources (cycles,
39 disk space) in order to permit a SMTP server and associated local
40 mail delivery system to be kept resident and continuously running.
41 Similarly, it may be expensive (or impossible) to keep a personal
42 computer interconnected to an IP-style network for long amounts of
43 time (the node is lacking the resource known as "connectivity").
45 Despite this, it is often very useful to be able to manage mail on
46 these smaller nodes, and they often support a user agent (UA) to aid
47 the tasks of mail handling. To solve this problem, a node which can
48 support an MTS entity offers a maildrop service to these less endowed
49 nodes. The Post Office Protocol - Version 3 (POP3) is intended to
50 permit a workstation to dynamically access a maildrop on a server
51 host in a useful fashion. Usually, this means that the POP3 is used
52 to allow a workstation to retrieve mail that the server is holding
53 for it.
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63 For the remainder of this memo, the term "client host" refers to a
64 host making use of the POP3 service, while the term "server host"
65 refers to a host which offers the POP3 service.
67 A Short Digression
69 This memo does not specify how a client host enters mail into the
70 transport system, although a method consistent with the philosophy of
71 this memo is presented here:
73 When the user agent on a client host wishes to enter a message
74 into the transport system, it establishes an SMTP connection to
75 its relay host (this relay host could be, but need not be, the
76 POP3 server host for the client host).
78 If this method is followed, then the client host appears to the MTS
79 as a user agent, and should NOT be regarded as a "trusted" MTS entity
80 in any sense whatsoever. This concept, along with the role of the
81 POP3 as a part of a split-UA model is discussed later in this memo.
83 Initially, the server host starts the POP3 service by listening on
84 TCP port 110. When a client host wishes to make use of the service,
85 it establishes a TCP connection with the server host. When the
86 connection is established, the POP3 server sends a greeting. The
87 client and POP3 server then exchange commands and responses
88 (respectively) until the connection is closed or aborted.
90 Commands in the POP3 consist of a keyword possibly followed by an
91 argument. All commands are terminated by a CRLF pair.
93 Responses in the POP3 consist of a success indicator and a keyword
94 possibly followed by additional information. All responses are
95 terminated by a CRLF pair. There are currently two success
96 indicators: positive ("+OK") and negative ("-ERR").
98 Responses to certain commands are multi-line. In these cases, which
99 are clearly indicated below, after sending the first line of the
100 response and a CRLF, any additional lines are sent, each terminated
101 by a CRLF pair. When all lines of the response have been sent, a
102 final line is sent, consisting of a termination octet (decimal code
103 046, ".") and a CRLF pair. If any line of the multi-line response
104 begins with the termination octet, the line is "byte-stuffed" by
105 pre-pending the termination octet to that line of the response.
106 Hence a multi-line response is terminated with the five octets
107 "CRLF.CRLF". When examining a multi-line response, the client checks
108 to see if the line begins with the termination octet. If so and if
109 octets other than CRLF follow, the the first octet of the line (the
110 termination octet) is stripped away. If so and if CRLF immediately
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119 follows the termination character, then the response from the POP
120 server is ended and the line containing ".CRLF" is not considered
121 part of the multi-line response.
123 A POP3 session progresses through a number of states during its
124 lifetime. Once the TCP connection has been opened and the POP3
125 server has sent the greeting, the session enters the AUTHORIZATION
126 state. In this state, the client must identify itself to the POP3
127 server. Once the client has successfully done this, the server
128 acquires resources associated with the client's maildrop, and the
129 session enters the TRANSACTION state. In this state, the client
130 requests actions on the part of the POP3 server. When the client has
131 finished its transactions, the session enters the UPDATE state. In
132 this state, the POP3 server releases any resources acquired during
133 the TRANSACTION state and says goodbye. The TCP connection is then
134 closed.
136 The AUTHORIZATION State
138 Once the TCP connection has been opened by a POP3 client, the POP3
139 server issues a one line greeting. This can be any string terminated
140 by CRLF. An example might be:
142 S. +OK dewey POP3 server ready (Comments to: PostMaster@UDEL.EDU)
144 Note that this greeting is a POP3 reply. The POP3 server should
145 always give a positive response as the greeting.
147 The POP3 session is now in the AUTHORIZATION state. The client must
148 now issue the USER command. If the POP3 server responds with a
149 positive success indicator ("+OK"), then the client may issue either
150 the PASS command to complete the authorization, or the QUIT command
151 to terminate the POP3 session. If the POP3 server responds with a
152 negative success indicator ("-ERR") to the USER command, then the
153 client may either issue a new USER command or may issue the QUIT
154 command.
156 When the client issues the PASS command, the POP3 server uses the
157 argument pair from the USER and PASS commands to determine if the
158 client should be given access to the appropriate maildrop. If so,
159 the POP3 server then acquires an exclusive-access lock on the
160 maildrop. If the lock is successfully acquired, the POP3 server
161 parses the maildrop into individual messages (read note below),
162 determines the last message (if any) present in the maildrop that was
163 referenced by the RETR command, and responds with a positive success
164 indicator. The POP3 session now enters the TRANSACTION state. If
165 the lock can not be acquired or the client should is denied access to
166 the appropriate maildrop or the maildrop can't be parsed for some
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175 reason, the POP3 server responds with a negative success indicator.
176 (If a lock was acquired but the POP3 server intends to respond with a
177 negative success indicator, the POP3 server must release the lock
178 prior to rejecting the command.) At this point, the client may
179 either issue a new USER command and start again, or the client may
180 issue the QUIT command.
182 NOTE: Minimal implementations of the POP3 need only be
183 able to break a maildrop into its component messages;
184 they need NOT be able to parse individual messages.
185 More advanced implementations may wish to have this
186 capability, for reasons discussed later.
188 After the POP3 server has parsed the maildrop into individual
189 messages, it assigns a message-id to each message, and notes the size
190 of the message in octets. The first message in the maildrop is
191 assigned a message-id of "1", the second is assigned "2", and so on,
192 so that the n'th message in a maildrop is assigned a message-id of
193 "n". In POP3 commands and responses, all message-id's and message
194 sizes are expressed in base-10 (i.e., decimal).
196 It sets the "highest number accessed" to be that of the last message
197 referenced by the RETR command.
199 Here are summaries for the three POP3 commands discussed thus far:
201 USER name
202 Arguments: a server specific user-id (required)
203 Restrictions: may only be given in the AUTHORIZATION
204 state after the POP3 greeting or after an
205 unsuccessful USER or PASS command
206 Possible Responses:
207 +OK name is welcome here
208 -ERR never heard of name
209 Examples:
210 C: USER mrose
211 S: +OK mrose is a real hoopy frood
212 ...
213 C: USER frated
214 S: -ERR sorry, frated doesn't get his mail here
216 PASS string
217 Arguments: a server/user-id specific password (required)
218 Restrictions: may only be given in the AUTHORIZATION
219 state after a successful USER command
220 Possible Responses:
221 +OK maildrop locked and ready
222 -ERR invalid password
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231 -ERR unable to lock maildrop
232 Examples:
233 C: USER mrose
234 S: +OK mrose is a real hoopy frood
235 C: PASS secret
236 S: +OK mrose's maildrop has 2 messages
237 (320 octets)
238 ...
239 C: USER mrose
240 S: +OK mrose is a real hoopy frood
241 C: PASS secret
242 S: -ERR unable to lock mrose's maildrop, file
243 already locked
245 QUIT
246 Arguments: none
247 Restrictions: none
248 Possible Responses:
249 +OK
250 Examples:
251 C: QUIT
252 S: +OK dewey POP3 server signing off
255 The TRANSACTION State
257 Once the client has successfully identified itself to the POP3 server
258 and the POP3 server has locked and burst the appropriate maildrop,
259 the POP3 session is now in the TRANSACTION state. The client may now
260 issue any of the following POP3 commands repeatedly. After each
261 command, the POP3 server issues a response. Eventually, the client
262 issues the QUIT command and the POP3 session enters the UPDATE state.
264 Here are the POP3 commands valid in the TRANSACTION state:
266 STAT
267 Arguments: none
268 Restrictions: may only be given in the TRANSACTION state.
269 Discussion:
271 The POP3 server issues a positive response with a line
272 containing information for the maildrop. This line is
273 called a "drop listing" for that maildrop.
275 In order to simplify parsing, all POP3 servers are
276 required to use a certain format for drop listings.
277 The first octets present must indicate the number of
278 messages in the maildrop. Following this is the size
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287 of the maildrop in octets. This memo makes no
288 requirement on what follows the maildrop size.
289 Minimal implementations should just end that line of
290 the response with a CRLF pair. More advanced
291 implementations may include other information.
293 NOTE: This memo STRONGLY discourages
294 implementations from supplying additional
295 information in the drop listing. Other,
296 optional, facilities are discussed later on
297 which permit the client to parse the messages
298 in the maildrop.
300 Note that messages marked as deleted are not counted in
301 either total.
303 Possible Responses:
304 +OK nn mm
305 Examples:
306 C: STAT
307 S: +OK 2 320
309 LIST [msg]
310 Arguments: a message-id (optionally) If a message-id is
311 given, it may NOT refer to a message marked as
312 deleted.
313 Restrictions: may only be given in the TRANSACTION state.
314 Discussion:
316 If an argument was given and the POP3 server issues a
317 positive response with a line containing information
318 for that message. This line is called a "scan listing"
319 for that message.
321 If no argument was given and the POP3 server issues a
322 positive response, then the response given is
323 multi-line. After the initial +OK, for each message
324 in the maildrop, the POP3 server responds with a line
325 containing information for that message. This line
326 is called a "scan listing" for that message.
328 In order to simplify parsing, all POP3 servers are
329 required to use a certain format for scan listings.
330 The first octets present must be the message-id of
331 the message. Following the message-id is the size of
332 the message in octets. This memo makes no requirement
333 on what follows the message size in the scan listing.
334 Minimal implementations should just end that line of
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343 the response with a CRLF pair. More advanced
344 implementations may include other information, as
345 parsed from the message.
347 NOTE: This memo STRONGLY discourages
348 implementations from supplying additional
349 information in the scan listing. Other, optional,
350 facilities are discussed later on which permit
351 the client to parse the messages in the maildrop.
353 Note that messages marked as deleted are not listed.
355 Possible Responses:
356 +OK scan listing follows
357 -ERR no such message
358 Examples:
359 C: LIST
360 S: +OK 2 messages (320 octets)
361 S: 1 120
362 S: 2 200
363 S: .
364 ...
365 C: LIST 2
366 S: +OK 2 200
367 ...
368 C: LIST 3
369 S: -ERR no such message, only 2 messages in
370 maildrop
372 RETR msg
373 Arguments: a message-id (required) This message-id may
374 NOT refer to a message marked as deleted.
375 Restrictions: may only be given in the TRANSACTION state.
376 Discussion:
378 If the POP3 server issues a positive response, then the
379 response given is multi-line. After the initial +OK,
380 the POP3 server sends the message corresponding to the
381 given message-id, being careful to byte-stuff the
382 termination character (as with all multi-line
383 responses).
385 If the number associated with this message is higher
386 than the "highest number accessed" in the maildrop, the
387 POP3 server updates the "highest number accessed" to
388 the number associated with this message.
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399 Possible Responses:
400 +OK message follows
401 -ERR no such message
402 Examples:
403 C: RETR 1
404 S: +OK 120 octets
405 S: <the POP3 server sends the entire message here>
406 S: .
408 DELE msg
409 Arguments: a message-id (required) This message-id
410 may NOT refer to a message marked as deleted.
411 Restrictions: may only be given in the TRANSACTION state.
412 Discussion:
414 The POP3 server marks the message as deleted. Any
415 future reference to the message-id associated with the
416 message in a POP3 command generates an error. The POP3
417 server does not actually delete the message until the
418 POP3 session enters the UPDATE state.
420 If the number associated with this message is higher
421 than the "highest number accessed" in the maildrop,
422 the POP3 server updates the "highest number accessed"
423 to the number associated with this message.
425 Possible Responses:
426 +OK message deleted
427 -ERR no such message
428 Examples:
429 C: DELE 1
430 S: +OK message 1 deleted
431 ...
432 C: DELE 2
433 S: -ERR message 2 already deleted
435 NOOP
436 Arguments: none
437 Restrictions: may only be given in the TRANSACTION state.
438 Discussion:
440 The POP3 server does nothing, it merely replies with a
441 positive response.
443 Possible Responses:
444 +OK
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455 Examples:
456 C: NOOP
457 S: +OK
459 LAST
460 Arguments: none
461 Restrictions: may only be issued in the TRANSACTION state.
462 Discussion:
464 The POP3 server issues a positive response with a line
465 containing the highest message number which accessed.
466 Zero is returned in case no message in the maildrop has
467 been accessed during previous transactions. A client
468 may thereafter infer that messages, if any, numbered
469 greater than the response to the LAST command are
470 messages not yet accessed by the client.
472 Possible Response:
473 +OK nn
475 Examples:
476 C: STAT
477 S: +OK 4 320
478 C: LAST
479 S: +OK 1
480 C: RETR 3
481 S: +OK 120 octets
482 S: <the POP3 server sends the entire message
483 here>
484 S: .
485 C: LAST
486 S: +OK 3
487 C: DELE 2
488 S: +OK message 2 deleted
489 C: LAST
490 S: +OK 3
491 C: RSET
492 S: +OK
493 C: LAST
494 S: +OK 1
496 RSET
497 Arguments: none
498 Restrictions: may only be given in the TRANSACTION
499 state.
500 Discussion:
502 If any messages have been marked as deleted by the POP3
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511 server, they are unmarked. The POP3 server then
512 replies with a positive response. In addition, the
513 "highest number accessed" is also reset to the value
514 determined at the beginning of the POP3 session.
516 Possible Responses:
517 +OK
518 Examples:
519 C: RSET
520 S: +OK maildrop has 2 messages (320 octets)
524 The UPDATE State
526 When the client issues the QUIT command from the TRANSACTION state,
527 the POP3 session enters the UPDATE state. (Note that if the client
528 issues the QUIT command from the AUTHORIZATION state, the POP3
529 session terminates but does NOT enter the UPDATE state.)
531 QUIT
532 Arguments: none
533 Restrictions: none
534 Discussion:
536 The POP3 server removes all messages marked as deleted
537 from the maildrop. It then releases the
538 exclusive-access lock on the maildrop and replies as
539 to the success of
540 these operations. The TCP connection is then closed.
542 Possible Responses:
543 +OK
544 Examples:
545 C: QUIT
546 S: +OK dewey POP3 server signing off (maildrop
547 empty)
548 ...
549 C: QUIT
550 S: +OK dewey POP3 server signing off (2 messages
551 left)
552 ...
555 Optional POP3 Commands
557 The POP3 commands discussed above must be supported by all minimal
558 implementations of POP3 servers.
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567 The optional POP3 commands described below permit a POP3 client
568 greater freedom in message handling, while preserving a simple POP3
569 server implementation.
571 NOTE: This memo STRONGLY encourages implementations to
572 support these commands in lieu of developing augmented
573 drop and scan listings. In short, the philosophy of
574 this memo is to put intelligence in the part of the
575 POP3 client and not the POP3 server.
577 TOP msg n
578 Arguments: a message-id (required) and a number. This
579 message-id may NOT refer to a message marked as
580 deleted.
581 Restrictions: may only be given in the TRANSACTION state.
582 Discussion:
584 If the POP3 server issues a positive response, then
585 the response given is multi-line. After the initial
586 +OK, the POP3 server sends the headers of the message,
587 the blank line separating the headers from the body,
588 and then the number of lines indicated message's body,
589 being careful to byte-stuff the termination character
590 (as with all multi-line responses).
592 Note that if the number of lines requested by the POP3
593 client is greater than than the number of lines in the
594 body, then the POP3 server sends the entire message.
596 Possible Responses:
597 +OK top of message follows
598 -ERR no such message
599 Examples:
600 C: TOP 10
601 S: +OK
602 S: <the POP3 server sends the headers of the
603 message, a blank line, and the first 10 lines
604 of the body of the message>
605 S: .
606 ...
607 C: TOP 100
608 S: -ERR no such message
610 RPOP user
611 Arguments: a client specific user-id (required)
612 Restrictions: may only be given in the AUTHORIZATION
613 state after a successful USER command; in addition,
614 may only be given if the client used a reserved
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623 (privileged) TCP port to connect to the server.
624 Discussion:
626 The RPOP command may be used instead of the PASS
627 command to authenticate access to the maildrop. In
628 order for this command to be successful, the POP3
629 client must use a reserved TCP port (port < 1024) to
630 connect tothe server. The POP3 server uses the
631 argument pair from the USER and RPOP commands to
632 determine if the client should be given access to
633 the appropriate maildrop. Unlike the PASS command
634 however, the POP3 server considers if the remote user
635 specified by the RPOP command who resides on the POP3
636 client host is allowed to access the maildrop for the
637 user specified by the USER command (e.g., on Berkeley
638 UNIX, the .rhosts mechanism is used). With the
639 exception of this differing in authentication, this
640 command is identical to the PASS command.
642 Note that the use of this feature has allowed much wider
643 penetration into numerous hosts on local networks (and
644 sometimes remote networks) by those who gain illegal
645 access to computers by guessing passwords or otherwise
646 breaking into the system.
648 Possible Responses:
649 +OK maildrop locked and ready
650 -ERR permission denied
651 Examples:
652 C: USER mrose
653 S: +OK mrose is a real hoopy frood
654 C: RPOP mrose
655 S: +OK mrose's maildrop has 2 messages (320
656 octets)
658 Minimal POP3 Commands:
659 USER name valid in the AUTHORIZATION state
660 PASS string
661 QUIT
663 STAT valid in the TRANSACTION state
664 LIST [msg]
665 RETR msg
666 DELE msg
667 NOOP
668 LAST
669 RSET
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679 QUIT valid in the UPDATE state
681 Optional POP3 Commands:
682 RPOP user valid in the AUTHORIZATION state
684 TOP msg n valid in the TRANSACTION state
686 POP3 Replies:
687 +OK
688 -ERR
690 Note that with the exception of the STAT command, the reply given
691 by the POP3 server to any command is significant only to "+OK"
692 and "-ERR". Any text occurring after this reply may be ignored
693 by the client.
695 Example POP3 Session
697 S: <wait for connection on TCP port 110>
698 ...
699 C: <open connection>
700 S: +OK dewey POP3 server ready (Comments to: PostMaster@UDEL.EDU)
701 C: USER mrose
702 S: +OK mrose is a real hoopy frood
703 C: PASS secret
704 S: +OK mrose's maildrop has 2 messages (320 octets)
705 C: STAT
706 S: +OK 2 320
707 C: LIST
708 S: +OK 2 messages (320 octets)
709 S: 1 120
710 S: 2 200
711 S: .
712 C: RETR 1
713 S: +OK 120 octets
714 S: <the POP3 server sends message 1>
715 S: .
716 C: DELE 1
717 S: +OK message 1 deleted
718 C: RETR 2
719 S: +OK 200 octets
720 S: <the POP3 server sends message 2>
721 S: .
722 C: DELE 2
723 S: +OK message 2 deleted
724 C: QUIT
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735 S: +OK dewey POP3 server signing off (maildrop empty)
736 C: <close connection>
737 S: <wait for next connection>
739 Message Format
741 All messages transmitted during a POP3 session are assumed to conform
742 to the standard for the format of Internet text messages [RFC822].
744 It is important to note that the byte count for a message on the
745 server host may differ from the octet count assigned to that message
746 due to local conventions for designating end-of-line. Usually,
747 during the AUTHORIZATION state of the POP3 session, the POP3 client
748 can calculate the size of each message in octets when it parses the
749 maildrop into messages. For example, if the POP3 server host
750 internally represents end-of-line as a single character, then the
751 POP3 server simply counts each occurrence of this character in a
752 message as two octets. Note that lines in the message which start
753 with the termination octet need not be counted twice, since the POP3
754 client will remove all byte-stuffed termination characters when it
755 receives a multi-line response.
757 The POP and the Split-UA model
759 The underlying paradigm in which the POP3 functions is that of a
760 split-UA model. The POP3 client host, being a remote PC based
761 workstation, acts solely as a client to the message transport system.
762 It does not provide delivery/authentication services to others.
763 Hence, it is acting as a UA, on behalf of the person using the
764 workstation. Furthermore, the workstation uses SMTP to enter mail
765 into the MTS.
767 In this sense, we have two UA functions which interface to the
768 message transport system: Posting (SMTP) and Retrieval (POP3). The
769 entity which supports this type of environment is called a split-UA
770 (since the user agent is split between two hosts which must
771 interoperate to provide these functions).
773 ASIDE: Others might term this a remote-UA instead.
774 There are arguments supporting the use of both terms.
776 This memo has explicitly referenced TCP as the underlying transport
777 agent for the POP3. This need not be the case. In the MZnet split-
778 UA, for example, personal micro-computer systems are used which do
779 not have IP-style networking capability. To connect to the POP3
780 server host, a PC establishes a terminal connection using some simple
781 protocol (PhoneNet). A program on the PC drives the connection,
782 first establishing a login session as a normal user. The login shell
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791 for this pseudo-user is a program which drives the other half of the
792 terminal protocol and communicates with one of two servers. Although
793 MZnet can support several PCs, a single pseudo-user login is present
794 on the server host. The user-id and password for this pseudo-user
795 login is known to all members of MZnet. Hence, the first action of
796 the login shell, after starting the terminal protocol, is to demand a
797 USER/PASS authorization pair from the PC. This second level of
798 authorization is used to ascertain who is interacting with the MTS.
799 Although the server host is deemed to support a "trusted" MTS entity,
800 PCs in MZnet are not. Naturally, the USER/PASS authorization pair
801 for a PC is known only to the owner of the PC (in theory, at least).
803 After successfully verifying the identity of the client, a modified
804 SMTP server is started, and the PC posts mail with the server host.
805 After the QUIT command is given to the SMTP server and it terminates,
806 a modified POP3 server is started, and the PC retrieves mail from the
807 server host. After the QUIT command is given to the POP3 server and
808 it terminates, the login shell for the pseudo-user terminates the
809 terminal protocol and logs the job out. The PC then closes the
810 terminal connection to the server host.
812 The SMTP server used by MZnet is modified in the sense that it knows
813 that it's talking to a user agent and not a "trusted" entity in the
814 message transport system. Hence, it does performs the validation
815 activities normally performed by an entity in the MTS when it accepts
816 a message from a UA.
818 The POP3 server used by MZnet is modified in the sense that it does
819 not require a USER/PASS combination before entering the TRANSACTION
820 state. The reason for this (of course) is that the PC has already
821 identified itself during the second-level authorization step
822 described above.
824 NOTE: Truth in advertising laws require that the author
825 of this memo state that MZnet has not actually been
826 fully implemented. The concepts presented and proven
827 by the project led to the notion of the MZnet
828 split-slot model. This notion has inspired the
829 split-UA concept described in this memo, led to the
830 author's interest in the POP, and heavily influenced
831 the the description of the POP3 herein.
833 In fact, some UAs present in the Internet already support the notion
834 of posting directly to an SMTP server and retrieving mail directly
835 from a POP server, even if the POP server and client resided on the
836 same host!
838 ASIDE: this discussion raises an issue which this memo
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847 purposedly avoids: how does SMTP know that it's talking
848 to a "trusted" MTS entity?
850 References
852 [MZnet] Stefferud, E., J. Sweet, and T. Domae, "MZnet: Mail
853 Service for Personal Micro-Computer Systems",
854 Proceedings, IFIP 6.5 International Conference on
855 Computer Message Systems, Nottingham, U.K., May 1984.
857 [RFC821] Postel, J., "Simple Mail Transfer Protocol",
858 USC/Information Sciences Institute, August 1982.
860 [RFC822] Crocker, D., "Standard for the Format of ARPA-Internet
861 Text Messages", University of Delaware, August 1982.
863 [RFC937] Butler, M., J. Postel, D. Chase, J. Goldberger, and J.
864 Reynolds, "Post Office Protocol - Version 2", RFC 937,
865 USC/Information Sciences Institute, February 1985.
867 [RFC1010] Reynolds, J., and J. Postel, "Assigned Numbers", RFC
868 1010, USC/Information Sciences Institute, May 1987.
870 Author's Address:
873 Marshall Rose
874 The Wollongong Group
875 1129 San Antonio Rd.
876 Palo Alto, California 94303
878 Phone: (415) 962-7100
880 Email: MRose@TWG.COM
898 Rose [Page 16]