client
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... SMTP service by
defining a means whereby a server SMTP can inform a client SMTP as to
the service ...
... framework does not require
modification of existing SMTP clients or servers unless the features
of the service extensions are to be requested or provided.
...
... SMTP service. This memo
defines a means whereby both an extended SMTP client and server may
recognize each other as such and the server can inform the client as
...
... SMTP client and server may
recognize each other as such and the server can inform the client as
to the service extensions that it supports.
...
... EHLO command will result in the server SMTP
replying with code 503. A client SMTP must not cache any information
...
... cache any information
returned if the EHLO command succeeds. That is, a client SMTP must
issue the EHLO command ...
... EHLO
command, it will return code 250. This indicates that both the
server and client SMTP are in the initial state, that is, there is no
...
...
In the case of a failure response, the client SMTP should issue
either the HELO or QUIT command ...
...
In the case of any error response, the client SMTP should issue
either the HELO or QUIT command ...
... state after returning this code
(see section 4.1.1 of RFC 821std10(-> 2821prop)). The client SMTP may then issue
either a HELO or a QUIT command ...
... Nevertheless, in order to achieve maxmimum interoperablity it is
suggested that extended SMTP clients using EHLO be coded to check for
server connection closure ...
... connection closure after EHLO is sent, either before or after
returning a reply. If this happens the client must decide if the
operation can be successfully completed without using any SMTP
extensions. If it can a new connection ...
... can be worked around by sending a RSET after the failure response to
EHLO, then sending the HELO. Clients that do this should be aware
that many implementations will return a failure code (e.g., 503 Bad
sequence of commands) in response to the RSET. This code can be
...
... SMTP does
not implement the extensions specified here. The
client would normally send a HELO command and proceed
as specified in RFC 821std10(-> 2821prop). See section 4.7 for
...