service
Click on the red underlined text to get to the source
...
This memo defines a framework for extending the SMTP service by
defining a means whereby a server SMTP can inform a client ...
... client SMTP as to
the service extensions it supports. Extensions to the SMTP service
are registered with the IANA ...
... SMTP as to
the service extensions it supports. Extensions to the SMTP service
are registered with the IANA. This framework ...
... SMTP clients or servers unless the features
of the service extensions are to be requested or provided.
...
... SMTP is widely and robustly deployed, some parts of the
Internet community might wish to extend the SMTP service. This memo
defines a means whereby both an extended SMTP client and server ...
... recognize each other as such and the server can inform the client as
to the service extensions that it supports.
...
...
It must be emphasized that any extension to the SMTP service should
not be considered lightly. SMTP's strength comes primarily from its
...
... deployment, and interoperability costs. In many cases, the cost of
extending the SMTP service will likely outweigh the benefit.
...
... a registry of SMTP service extensions (section 5) ...
... EHLO command instead of the HELO command. If
the SMTP server supports the SMTP service extensions it will give a
successful response (see section 4.3), a failure response (see 4.4),
or an error response ...
... error response (4.5). If the SMTP server does not support any
SMTP service extensions it will generate an error response (see
section 4.5).
...
... STD 10, RFC 821std10(-> 2821prop) without
impacting existing services in any way. The minor changes needed are
enumerated below.
...
... The IANA maintains a registry of SMTP service extensions. Associated
with each such extension is a corresponding EHLO keyword value. Each
...
... with each such extension is a corresponding EHLO keyword value. Each
service extension registered with the IANA must be defined in an RFC.
Such RFCs must either be on the standards-track ...
... the textual name of the SMTP service extension;
...
... EHLO keyword value that starts with an upper or
lower case "X" refers to a local SMTP service extension, which is
used through bilateral, rather than standardized, agreement. Keywords
...
... used through bilateral, rather than standardized, agreement. Keywords
beginning with "X" may not be used in a registered service extension.
...
... IESG-
approved experimental SMTP service extension registered with IANA. A
conforming server must not offer non "X" prefixed keyword values that
...
...
If for some reason the server SMTP is unable to list the service
extensions it supports, it will return code 554.
...
...
If the server SMTP determines that the SMTP service is no longer
available (e.g., due to imminent system shutdown), it will return
code 421.
...
...
Service Ext EHLO Keyword Parameters Verb Added Behavior
------------- ------------ ---------- ---------- ------------------
...
... headers of all messages they receive. A "with ESMTP" clause
should be added to this field when any SMTP service extensions are
used. "ESMTP" is hereby added to the list of standard protocol names
...
... C: <open connection to server>
S: 220 dbc.mtview.ca.us SMTP service ready
C: EHLO ymir.claremont.edu
...
... C: <open connection to server>
S: 220 dbc.mtview.ca.us SMTP service ready
C: EHLO ymir.claremont.edu
...
... SMTP also implements the SMTP
EXPN and HELP commands, one standard service extension
(8BITMIME), and two nonstandard and unregistered ...
... 8BITMIME), and two nonstandard and unregistered
service extensions (XONE and XVRB).
(3) Finally, a server that does not support SMTP service ...
... service extensions (XONE and XVRB).
(3) Finally, a server that does not support SMTP service
extensions would act as follows:
...
... C: <open connection to server>
S: 220 dbc.mtview.ca.us SMTP service ready
C: EHLO ymir.claremont.edu
...
... to the EHLO verb. However, all information provided by announcement
of any of the initial set of service extensions defined by this RFC
can be readily deduced by selective probing of the verbs required to
transport ...
... transport and deliver mail. The security implications of service
extensions described in other RFCs should be dealt with in those
RFCs.
...