Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRONIC MAIL SERVER
FIELD OF THE INVENTION
The present invention relates to a system and method for facilitating the
transmission
and delivery of electronic mail over a wide area network. In particular, the
present
invention relates to an electronic mail server configured to recognize e-mail
account
identifiers consisting of non-ASCII characters.
BACKGROUND OF THE INVENTION
In order to facilitate communication between communication devices over a
network,
each network device is typically assigned a unique numeric network address. A
user
associated with one of the network devices then need only provide the network
transport layer with the numeric network address of the intended target to
communicate with the target. Although this system functions satisfactorily in
small
network where users only communicate with a small number of network
communication devices, the system cannot be readily transported to large
networks
since it would require each network user to remember a large number of unique
numeric network addresses. For this reason, the domain name system (DNS) was
proposed by Mockapetris in 1987 (RFC 1034 and RFC 1035, Network Working
Group; presently available at "http://www.ietf.org") as a mechanism for
facilitating
communication between communication devices over the Internet.
The DNS facilitates Internet communication by associating domain names with
the
numeric (IP, "Internet Protocol") network addresses. The DNS basically
consists of
resource records, domain name servers, and resolvers. Each resource records
includes
information concerning each network node, including the IP address of the
network
node, and the domain names associated with the IP address. Together, the
resource
records provide the Internet with a tree-structured domain name space. Domain
name
servers are Internet servers which retain information concerning the domain
name
space. In particular, each domain name server has a file ("zone file") which
retains
resource records associated with its own subset of the domain name space.
These
records are referred to as "authoritative"records. Also, through queries from
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resolvers, domain name servers also temporarily cache copies of resource
records
acquired from other domain name servers in order to improve the performance of
the
retrieval process when non-local data is requested by a resolver. Resolvers
are local
programs which extract information from domain name servers in response to
client
requests.
Typically, the domain name associated with a network device at particular IP
address
has a top level label field, and one or more lower level label fields. The
label fields
comprising a domain name are separated from one another through a delimiter
("."),
and are each positioned in the domain name according to their respective
relative
levels in the domain name hierarchy. To transmit an e-mail message to a
recipient
having an e-mail account subsisting at a remote network device, using the
originator's
local computer the originator of the e-mail message provides its e-mail server
with the
electronic mail message, together with the originator's name, the domain name
of the
e-mail server in which the originator has established an e-mail account, the
recipient's
name, and the domain name of the e-mail server in which the recipient has
established
an e-mail account. In effect, each e-mail account is represented on a e-mail
server as a
distinct directory, each containing a sub-directory for caching incoming e-
mail
messages and a sub-directory for caching outgoing e-mail messages.
Upon receipt of the e-mail message from the originator, the originator's e-
mail server
assigns a globally unique message identifier (determined in accordance with
the time
of receipt of the e-mail message), extracts the domain name of the recipient's
e-mail
server from the e-mail message, and transmits the extracted domain name to a
domain
name resolver for determination of the IP address of the recipient's e-mail
server. The
resolver queries a root DNS server with the top level label identified in the
domain
name to obtain the IP address of the DNS server which has the zone file
associated
with the top level domain. The resolver then accesses the identified DNS
server using
the obtained IP address, and with the label occupying the next highest
position in the
domain name hierarchy (the label immediately to the left of the top level
label in the
domain name) obtains the IP address of the DNS server which has the zone file
associated with the queried label. The process continues until each label in
the
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domain name has been resolved, at which point the last queried DNS server
provides
the resolver with the IP address of the network device having the specified
domain
name. The resolver then transmits the received IP address to the originator's
e-mail
server.
Upon receipt of the IP address assigned to the recipient's e-mail server, the
originator's
e-mail server establishes a communications channel with the recipient's e-mail
server
and then transmits the e-mail message over the communications channel,
typically
using Simple Mail Transfer Protocol (commonly referred to as "SMTP"; described
in
detail in RFC 821 and RFC 1869, "http://www.ietf.org"). After an initial
handshaking
stage during which the recipient's e-mail server acknowledges that it is
willing to
receive an e-mail message and that the recipient has established an e-mail
account
thereon, the originator's e-mail server transmits the e-mail message to the
recipient's e-
mail server and then closes the communications channel. Upon receipt of the e-
mail
message, the recipient's e-mail server caches the e-mail message in the
directory
associated with the recipient.
To retrieve the e-mail message, the recipient establishes a communications
channel
with the recipient's e-mail server, and retrieves the e-mail message over the
communications channel, typically using Post Office Protocol - Version 3
(commonly
referred to as "POP3"; described in detail in RFC 1939 and RFC 2449,
"http://www.ietf.org"). Again, after an initial handshaking stage, during
which the
recipient's e-mail server acknowledges that it is ready to transmit e-mail
messages to
the recipient, the recipient authenticates itself with the e-mail server using
an assigned
username and password. After the recipient successfully authenticates itself,
the
recipient is then able to initiate transmission of the e-mail message over the
communications channel to the recipient's local computer.
Although e-mail systems have been implemented successfully worldwide, using
SMTP and POP3, conventional e-mail systems suffers from at least three main
deficiencies. First, the domain names implemented by the DNS must follow the
rules
for ARPANET host names. Consequently, each domain name label associated with
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an e-mail server must begin and end with a "letter" or one of the numbers 0 to
9, and
contain only "letters", the numbers 0 to 9 or a hyphen in between. Further,
each
"letter" can only be one of 'A' to 'Z' and 'a' to 'z'. As a result, the number
of domain
names available is severely limited. Second, the DNS system is case
insensitive, so
that two domain names which have identical spellings but whose component
letters do
not correspond in terms of their respective cases, will resolve to the same
network
address. Third, most e-mail servers only accept, for inclusion as part of an e-
mail
account name, the hyphen, the numbers 0 to 9 and the letters 'A' to 'Z' and
'a' to 'z',
thereby limiting the number of account names available.
Therefore, there remains a need for an electronic mail system which expands
upon the
number and type of characters available for the account name component and the
domain name component of e-mail addresses.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an
electronic
mail server and a method for facilitating e-mail communication over a network
which
address deficiencies of the prior art electronic mail systems.
The electronic mail server, according to the first aspect of the invention,
includes an
account name database and an account name processor in communication with the
account name database for providing a response to a message received over the
network. Typically, the message includes an e-mail account name label
comprising at
least one account name character (having an account name character set type),
with
the character set type including a non-ASCII compatible character set. The
account
name database includes a number of database records, each identifying an e-
mail
account name comprising at least one record character having a record
character set
type, and a record character set identifier identifying the record character
set type.
The account name processor includes a correlation processor and a response
processor. The correlation processor is configured to determine the
correlation
between the received e-mail account name label and the respective e-mail
account
names in accordance with the associated character set type. The response
processor is
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in communication with the correlation processor and provides the response to
the
message in accordance with the correlation indication.
The method for facilitating e-mail communication, according to the first
aspect of the
invention, includes the steps of (1) receiving at an e-mail server a message
comprising
an e-mail account name label, the e-mail server maintaining at least one e-
mail
account each associated with an e-mail account name, with the account name
label
comprising at least one account name character having an account name
character set
type and with the character set type including a non-ASCII compatible
character set;
(2) determining the correlation between the received e-mail account name label
and
the respective e-mail account names in accordance with the associated
character set
type; and (3) responding to the message in accordance with the correlation
indication.
According to a second aspect of the present invention, there is provided an
electronic
message for facilitating electronic communication. The electronic message,
according
to the second aspect of the invention, includes a header portion and a data
portion
associated with the header portion. The header portion includes an e-mail
account
name label, with the account name label comprising at least one account name
character (having an account name character set type), and with the character
set type
including a non-ASCII compatible character set. The data portion includes an
originator field identifying an originator of the message and a recipient
field
identifying a recipient of the message, with one of the fields being
associated with the
e-mail account name label.
According to a third aspect of the present invention, there is provided an
electronic
mail account name database for facilitating electronic communication. The
account
name database, according to the third aspect of the invention, includes at
least one
database record, each comprising (1) an account name label associated with an
e-mail
account name, with the account name label including at least one record
character
having a record character set type; and (2) a record character set identifier
identifying
the record character set type.
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BRIEF DESCRIPTION OF THE DRAW1IVGS
The preferred embodiment of the invention will now be described, by way of
example
only, with reference to the drawings, in which:
Fig. 1 is a schematic view of an electronic mail system, according to the
present
invention, depicting a plurality of network clients, a plurality of e-mail
transmission
servers, a plurality of e-mail delivery servers, and a communications network
interconnecting the network clients and the e-mail servers;
Fig. 2 is a schematic view of the e-mail transmission server shown in Fig. 1,
depicting
the account name database, and the correlation processor and the response
processor
of the account name processor;
Fig. 3 is a schematic diagram of a sample record comprising the account name
database;
Fig. 4 is a schematic diagram of a sample e-mail message which can be
transmitted
between e-mail servers;
Fig. 5 is a schematic view of the e-mail delivery server shown in Fig. 1,
depicting the
account name database, and the correlation processor and the response
processor of
the account name processor; and
Figs. 6a and 6b together comprise a flow chart depicting the sequence of steps
executed by the e-mail servers in transmitting an electronic mail message
between
network clients over the communications network.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning to Fig. 1, an electronic mail system, denoted generally as 100, is
shown
comprising a plurality of network clients 102, a plurality of a plurality of
name
resolution servers 104, a plurality of network address servers 106, a
plurality of e-mail
transmission servers 200, a plurality of e-mail delivery servers 500, and a
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communications network 108 interconnecting the network clients 102, the name
resolution servers 104, the network address servers 106, the e-mail
transmission
servers 200 and the e-mail delivery servers 500. Preferably, the
communications
network 108 comprises the Internet, the e-mail transmission servers 200
comprise
SMTP-based servers and the e-mail delivery servers 500 comprise POP3-based
servers. However, the communications network 108 may also comprise other
network forms, such as an intranet or a wireless network, and the e-mail
servers 200,
500 may employ protocols other than SMTP and POP3, if desired. Further, each e-
mail transmission server 200 may be paired with an e-mail delivery servers
500, with
both servers S00 residing on a common computer.
Preferably, each network client 102 comprises a personal computer equipped
with
software for communicating with the name resolution servers 104 and the e-mail
servers 200, 500 over the communications network 108. Further, preferably the
name
resolution servers 104 and the network address servers 106 respectively
comprise
domain name resolvers and domain name servers, as described by Mockapetris in
RFC 1034 and RFC 1035. Since RFC 1034 and RFC 1035 are publicly available
documents, and since the structure and operation of domain name resolvers and
domain name servers are well known to those skilled in the art, no description
of the
name resolution servers 104 and the network address servers 106 is required.
As shown in Fig. 2, each e-mail transmission server 200 comprises a network
interface 202 for communicating with the network clients 102 and other e-mail
transmission servers 200 over the communications network 108, and a central
processing unit (CPU) 204 in communication with the network interface 202, and
a
non-volatile memory (NVM) 206 and a volatile memory (RAM) 208 in
communication with the CPU 204. Preferably the NVM 206 comprises a magnetic or
optical storage device, and includes a non-volatile account name database 210
which
has records identifying each e-mail account managed by the e-mail transmission
server 200, and an e-mail message database 212 which stores e-mail messages
received from network clients 102. Consistent with the structure of SMTP-based
e-
mail servers, the e-mail message database 212 comprises a plurality of
directories or
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electronic folders, each being associated with a respective e-mail account and
including an inbox sub-directory and an outbox sub-directory.
The NVM 206 also includes processor instructions for the CPU 204 which
establish
S in the RAM 208 a volatile account name database 214 as a copy of the non-
volatile
account name database 210, and a memory object defining an account name
processor
216 in communication with the account name database 214. As will be
appreciated,
the account name database 214 is established in the RAM 208 to increase the
speed of
the account name resolving process and may be dispensed with in applications
where
speed is not a paramount concern.
The account name database 214 of each e-mail transmission server 200 includes
a
plurality of database records 300, each being associated with an e-mail
account. The
structure of a typical database record is shown in Fig. 3. As shown, each
database
record 300 includes a plurality of characters 302 which together define an e-
mail
account name 304a, and a character set identifier 306a identifying the
character set of
which the characters 302 comprising the e-mail account name 304a are members.
However, it will be appreciated that the character codes used to define an e-
mail
account name using one character set could define another e-mail account name
using
another character set. Accordingly, to allow the e-mail transmission server
200 to
communicate with other SMTP servers which do not comply with the account name
resolving process described below (ie. do not transmit a character set
identifier to
identify the character set used to define the username component of an e-mail
address), preferably each database record 300 includes a plurality of alias e-
mail
account names 304b, 304c, 304d each having an associated (different) character
set
identifier (306b, 306c, 306d).
In the example shown, the e-mail account names 304a, 304b use the same
character
codes, but employ different character sets (Chinese character sets BigS and
GB2312)
to define the respective e-mail account names. The e-mail account names 304a,
304c
employ different character sets (Chinese Character sets BigS and GB2312), but
define
the same account name using different character codes. The e-mail account
names
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304c, 304d again employ different character sets (Chinese Character sets BigS
and
GB2312), but use the same character codes to define different account names.
As will
be explained below, by uniquely associating each e-mail account with an e-mail
account name 304a and a plurality of e-mail account name aliases 304b, 304c,
304d,
the e-mail transmission server 200 is able to resolve an account name defined
using
any of a plurality of different character sets, even if the e-mail address
received does
not include a character set identifier (described below). However, it is a
goal of the
electronic mail system 100 to eventually standardize the character set used by
all e-
mail servers to a multinational character set, such as a Unicode-based
character set, so
that any account name can be defined in any language without reference to a
character
set identifier. Consequently, it will be appreciated that the use of a
character set
identifier 306 and e-mail account aliases 304b, 304c, 304d are transitional
measures to
be used until such time as a standard is established for the multinational
character set.
Turning again to Fig. 2, the account name processor 216 is shown comprising a
correlation processor 218 and a response processor 220 in communication with
the
correlation processor 218. The correlation processor 218 is configured to
determine a
correlation between the account name component of an e-mail address, and the
account names 304 identified in the account name database 214. In other words,
the
correlation processor 218 of each e-mail transmission server 200 is configured
to
determine whether an e-mail account name component of an e-mail message
received
over the communications network 108 has a corresponding entry in the e-mail
transmission server's 200 account name database 214. The response processor
220 is
configured to provide a response to the received e-mail message in accordance
with
the correlation indication.
Preferably, each e-mail transmission server 200 is configured to recognize a
plurality
of different character sets, including a non-ASCII compatible character set
(such as
UTF-8: an 8-bit Unicode-based character set) to facilitate communication of e-
mails
(having multinational characters in the account name fields) with 8-bit e-mail
servers.
Further, preferably each e-mail transmission server 200 is configured to
recognize a 7-
bit ACE (ASCII Compatible Encoding) character set for backwards compatibility
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with 7-bit e-mail servers. However, as discussed above, it is a goal of the
electronic
mail system 100 to standardize the character set used by all e-mail servers to
a
multinational character set, such as a Unicode-based character set, so that
any account
name can be defined in any language without reference to a character set
identifier.
Consequently, it will be appreciated that the use of an ACE character set is a
transitional measure to be used until such time as a standard is established
for the
multinational character set and all e-mail servers are capable of recognizing
account
names encoded with the multinational character set.
The structure of an e-mail message 400 (which could be transmitted between an
originating e-mail transmission server 200 and a recipient e-mail transmission
server
200) is shown in Fig. 4. As will be apparent, the e-mail message 400 is
similar to the
standard message format for Internet text messages described in detail in RFC
822
(available at "http://www.ietf.org") in that the e-mail message 400 includes a
message
ID 402, a text header portion 404 and a text body or data portion 406
associated with
the header portion 404. The header portion 404 includes a plurality of header
lines
408, each including a field identifier 410, a plurality of characters 412
which define an
account "nickname" 414, and a plurality of characters 416 associated with the
field
identifier 410 which define an e-mail account name 418.
The account names 418 respectively associated with the "M-FROM" and "M-
REPLY-TO" field identifiers 410 are used by the e-mail transmission server 200
for
the representation of account names using multinational characters. In
particular, the
"M-FROM" field identifier 410 defines the account name of the originator of
the e-
mail message, while the "M-REPLY-TO" field identifier 410 defines the account
name to which replies should be transmitted. The "FROM" and "REPLY-TO" field
identifiers 410 serve a similar purpose respectively as the "M-FROM" and "M-
REPLY-TO" field identifiers 410, except that the account names associated with
the
"FROM" and "REPLY-TO" field identifiers 410 are defining using an ACE
character
set to ensure backwards compatibility with non-compliant client servers 102.
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The e-mail delivery server 500 is substantially similar in structure to the e-
mail
transmission server 200. As shown in Fig. 5, each e-mail delivery server 500
comprises a network interface 502 for communicating with the network clients
102
and the e-mail transmission servers 200 over the communications network 108,
and a
central processing unit (CPU) 504 in communication with the network interface
502,
and a non-volatile memory (NVM) 506 and a volatile memory (RAM) 508 in
communication with the CPU 504. Preferably the NVM 506 comprises a magnetic or
optical storage device, and includes a non-volatile account name database 510
which
has records identifying each e-mail account managed by the e-mail delivery
server
500, and a message database 512 for caching incoming e-mail messages.
The NVM 506 also includes processor instructions for the CPU 504 which
establish
in the RAM 508 a volatile account name database 514 as a copy of the non-
volatile
account name database 510, and a memory object defining an account name
processor
516 in communication with the account name database 514. The account name
database 514 of each e-mail delivery server 500 includes a plurality of
database
records 300, each being associated with an e-mail account. The account name
processor 516 is shown comprising a correlation processor 518 and a response
processor 520 in communication with the correlation processor 518. The
correlation
processor 518 is configured to determine a correlation between an account name
received from a user of a network client 102, and the account names identified
in the
account name database 514 to determine whether the received account name is
valid.
The response processor 520 is configured to provide a response to the network
client
102 in accordance with the correlation indication.
The operation of the electronic mail system 100 will now be described with
reference
to Figs. 6a and 6b. Once the e-mail servers 200, 500 are deployed, upon power-
up
each e-mail server 200, 500 reads its respective database into its respective
RAM.
Then, at step 500, one of the network clients 102 causes one of the e-mail
transmission servers 200 (the "originating" e-mail transmission server 200) to
open a
communications channel with another one of the e-mail transmission servers 200
(the
"receiving" e-mail transmission server 200) over the communications network
108 in
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order to send an e-mail message 400 to a recipient having an e-mail account
established at the receiving e-mail transmission server 200. Consistent with
the
SMTP protocol, preferably each e-mail transmission server 200 is configured to
wait
for a connection on TCP port 25 for the initiation of an e-mail transmission
request.
S
Once a communications channel is established, at step 502 the originating
server 200
transmits a command to the receiving server 200, requesting that the receiving
server
200 indicate whether it is capable of processing e-mail messages 400 having e-
mail
addresses incorporating multilingual characters and, if so, to provide the
originating
server 200 with a list of character sets recognized by the receiving server
200. In
effect, at step 502 the originating server 200 attempts to negotiate a
suitable character
set with the receiving server 200. At step 504, the originating server 200
selects one
of the identified character sets and transmits a "MAIL FROM" command to the
receiving server 200, together with the account name of the originator of the
e-mail
message 400 encoded in the selected character set and a "CHARSET" parameter
defining the selected character set.
Upon receipt of the account name and the associated "CHARSET" parameter, at
step
506 the account name processor 216 of the receiving server 200 determines
whether
the received "CHARSET" parameter identifies one of the character sets
recognized by
the receiving server 200. If the "CHARSET" parameter is recognized, the
receiving
server 200 replies with a positive acknowledgement, whereas if the "CHARSET"
parameter is not recognized, the receiving server 200 replies with an error
message.
After the appropriate character set is negotiated, at step 508 the originating
server 200
transmits a "RCPT TO" command to the receiving server 200, together with the
account name of the recipient of the e-mail message 400 encoded in the
selected
character set. Upon receipt of the account name, at step 510 the account name
processor 216 of the receiving server 200 queries its account name database
214 with
the received account name and the "CHARSET" parameter to determine whether the
account name is valid. Alternately, if the originating server 200 does not
provide the
"CHARSET" parameter, the account name processor 216 of the receiving server
200
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queries its account name database 214 with the received account name for an
entry
which matches an e-mail account name 304a or one of the alias account names
304b,
304c, 304d.
Upon receipt of a positive response from the receiving server 200, at step 512
the
originating server 200 transmits the data portion of the e-mail message 400 to
the
receiving server 200 and then closes the communications channel with the
receiving
server 200. Alternately, in one variation, the originating server 200 only
transmits the
header portion 404 to the receiving server 200, together with a pointer to the
data
portion 406 where the data portion 406 is stored in the e-mail message
database 212
on the originating server 200. This variation is particularly advantageous
where the
originator of the e-mail message 400 identifies several recipients for the e-
mail
message 400, all who have e-mail accounts established on the same receiving
server
200 since it conserves disk space on the receiving server 200. Alternately, in
yet
another variation, the originating server 200 transmits the header portion 404
and the
data portion 406 to the receiving server 200, and the receiving server 200
maintains in
its e-mail message database 212 a single copy of the received e-mail message
400,
and then provides the e-mail delivery server 500 with the header portion 404
and a
pointer to the data portion 406 where the data portion 406 is stored in the e-
mail
message database 212 on the receiving server 200.
A sample SMTP session between an originating e-mail transmission server 200
(C)
and a receiving e-mail transmission server 200 (S) is shown below, with the
command
"EHLO" being a command from the SMTP-extension, requesting a listing of
supported modes and character sets from the receiving server 200. The selected
character set is UTF-8, and the response "MATRX" to the "EHLO" command
identifies that the receiving server 200 is compliant with the subject
protocol:
S: <wait for connection on TCP port 25>
C: <open connection to server>
S: 220 mail.neteka.com -- Server SMTP (NeBOX v1.1)
C: EHLO mail.toronto.edu
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S: 250-mail.neteka.com
S: 250-8BITMIME
S: 250 MATRX UTF-8 GB2312
C: MAIL FROM:<(E4 E8 AD E6 96 87)@toronto.edu> CHARSET=UTF-8
S: 250 Address Ok.
C: RCPT TO:<david@neteka.com>
S: 250 david@neteka.com OK
C: DATA
Another sample SMTP session is shown below, where the selected character set
is not
supported by the receiving server 200:
C: EHLO mail.toronto.edu
S: 250-mail.neteka.com
S: 250-8BITMIME
S: 250 MATRX UTF-8 GB2312
C: MAIL FROM:<(A4 A4 A4 E5)@neteka.com> CHARSET=BigS
S: 504 command parameter not implemented
C: MAIL FROM:<(E4 E8 AD E6 96 87)@neteka.com> CHARSET=UTF-8
S: 250 Address Ok.
Alternately, in one variation, the "CHARSET" parameter is dispensed with, and
the
"MAIL FROM" and "RCPT TO" commands are respectively replaced with the "M-
MAIL FROM" and "M-RCPT TO" commands which indicate by way of implication
that the UTF-8 character set is selected. A sample SMTP session using these
additional commands is shown below:
C: EHLO mail.toronto.edu
S: 250-mail.neteka.com
S: 250-8BITMIME
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S: 250 MATRX
C: M-MAIL FROM:<(E4 E8 AD E6 96 87)@neteka.com>
S: 250 Address Ok.
If, at step 502, the originating server 200 determines that the receiving
server 200 is
not capable of processing e-mail messages 400 having e-mail addresses
incorporating
multilingual characters, the originating server 200 should attempt to send any
multilingual names in ACE format. Thus, in the following SMTP session example,
the originating server 200 transmits a BIGS-encoded account name encoded in
RACE
format:
S: 220 mail.example.com - Server SMTP
C: EHLO mail.neteka.com
S: 500 Command not recognized: EHLO
C: HELD mail.neteka.com
S: 250 mail.example.com hello
C: MAIL FROM:<bq--3bhc2zmh@neteka.com>
S: 250 Address Ok.
...
In order for the e-mail message 400 to be delivered to the recipient after
transmission
to the receiving server 200, at step 514 the receiving e-mail transmission
server 200
opens a communications channel with one of the e-mail delivery servers 500.
Consistent with the POP3 protocol, preferably each e-mail delivery server 500
is
configured to wait for a connection on TCP port 110 for the initiation of an e-
mail
delivery request.
Once a communications channel is established, at step 516 the receiving server
200
transmits a command to the delivery server 500, requesting that the delivery
server
500 indicate whether it is capable of processing e-mail messages 400 having e-
mail
addresses incorporating multilingual characters and, if so, to provide the
receiving
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server 200 with a list of character sets recognized by the delivery server
500. In
effect, at step 516 the receiving server 200 attempts to negotiate a suitable
character
set with the delivery server 500. At step 518, the receiving server 200
selects one of
the identified character sets and transmits a "USER" command to the delivery
server
500, together with the account name of the recipient of the e-mail message 400
encoded in the selected character set and a "CHARSET" parameter defining the
selected character set.
Upon receipt of the account name and the associated "CHARSET" parameter, at
step
520 the account name processor 516 of the delivery server 500 determines
whether
the received "CHARSET" parameter identifies one of the character sets
recognized by
the delivery server 500. If the "CHARSET" parameter is recognized, the account
name processor 516 queries its account name database 514 with the received
account
name and the "CHARSET" parameter to determine whether the account name is
valid. At step 522, the receiving server 200 then transmits the e-mail message
400 (or
the header portion 404 and a pointer to the data portion 406, as discussed
above) to
the delivery server 500, and closes the communications channel with the
delivery
server 500.
A sample POP3 session between a receiving e-mail transmission server 200 (C)
and
an e-mail delivery server 500 (S) is shown below, with the command "CAPA"
being a
command from the POP3-extension, requesting a listing of supported modes and
character sets from the delivery server 500:
S: +0K POP3 server ready
C: CAPA
S: +0K Capability list follows
S: TOP
S: USER
S: MATRX UTF-8 GB2312
S:.
C: USER (A4 A4 A4 ES)@neteka.com CHARSET=BigS
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S: -ERR CHARSET=big5 not implemented
C: USER (E4 E8 AD E6 96 87)@neteka.com CHARSET=UTF-8
S : +0K welcome
The present invention is defined by the claims appended hereto, with the
foregoing
description being illustrative of the preferred embodiment of the invention.
Those of
ordinary skill may envisage certain additions, deletions and/or modifications
to the
described embodiment, which although not explicitly described herein, do not
depart
from the spirit or scope of the invention, as defined by the appended claims.
