transport
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... data stream channel. While this
document specifically discusses transport over TCP, other transports
...
... document specifically discusses transport over TCP, other transports
are possible. Appendices to RFC 821std10(-> 2821prop) describe some of them.
...
...
An important feature of SMTP is its capability to transport mail
across networks, usually referred to as "SMTP ...
... WAN
environment utilizing a non-TCP transport-level protocol. Using
SMTP, a process can transfer mail to another process on the same
...
... protocols, or when the SMTP client is inside an isolated transport
service environment, the domain name determined will identify an
intermediate destination ...
... receiving the message) or "gateway" (that is, it may
transport the message further using some protocol other than SMTP).
SMTP ...
... host when the
two hosts are connected to the same transport service. When they are
not connected to the same transport service, transmission occurs via
...
... hosts are connected to the same transport service. When they are
not connected to the same transport service, transmission occurs via
one or more relay SMTP servers. An intermediate host ...
...
SMTP transports a mail object. A mail object contains an envelope
and content.
...
... particular, SMTP servers and clients provide a mail transport service
and therefore act as "Mail Transfer Agents" (MTAs ...
... originator) introduces mail into the Internet or, more generally,
into a transport service environment. A "delivery" SMTP system is
...
... delivery" SMTP system is
one that receives mail from a transport service environment and
passes it to a mail user agent or deposits ...
... gateway")
receives mail from a client system in one transport environment and
transmits it to a server system in another transport environment.
...
... client system in one transport environment and
transmits it to a server system in another transport environment.
Differences in protocols or message semantics between the transport ...
... transport environment.
Differences in protocols or message semantics between the transport
environments on either side of a gateway may require that the gateway ...
... long history of problems when intermediate hosts have attempted to
optimize transport by modifying them, the local-part MUST be
interpreted and assigned semantics only by the host ...
... Commands and replies are composed of characters from the ASCII
character set [1]. When the transport service provides an 8-bit byte
(octet) transmission channel ...
... Internet
SMTP transport service environment, MX records or various forms of
explicit routing may require that an intermediate SMTP server ...
... routing may require that an intermediate SMTP server perform
a translation function between one transport service and another. As
discussed in section 2.3.8, when such a system is at the boundary
between two transport service ...
... transport service and another. As
discussed in section 2.3.8, when such a system is at the boundary
between two transport service environments, we refer to it as a
"gateway" or "gateway ...
... 822std11(-> 2822prop) syntax with non-SMTP transports SHOULD designate an unambiguous
address, associated with the transport ...
... transports SHOULD designate an unambiguous
address, associated with the transport envelope, to which error
reports (e.g., non-delivery messages) should be sent.
...
... return-path header,
unless it is known that the "elsewhere" transport also uses
Internet domain ...
... the SMTP envelope or combine it with information present in the
envelope of the other transport system to construct the reverse
path argument to the MAIL command in the SMTP ...
... Internet Assigned Numbers Authority (IANA). "Via" is primarily of value with non-Internet transports. SMTP servers SHOULD NOT use unregistered names. ...
... final delivery of the message, or hand it off using some mechanism
outside the SMTP-provided transport environment. Of course, neither
of the latter require that the list of MX records be examined
further.
...
... authenticated, or
integrity checks provided, at the transport level. Real mail
security lies only in end-to-end ...
... protocol extensions and configuration options that provide
authentication at the transport level (e.g., from an SMTP client to
...
... role of a revised standard for
Internet mail transport, and many contributors helped form the
wording in this specification. The hundreds of participants in the
many discussions ...
... A. TCP Transport Service ...
... As each relay host adds itself to the beginning of the list, it MUST
use its name as known in the transport environment to which it is
relaying the mail rather than that of the transport environment from
...
... use its name as known in the transport environment to which it is
relaying the mail rather than that of the transport environment from
which the mail came (if they are different).
...