On Wed, 2020-03-04 at 10:10 +0100, Alessandro Vesely wrote:
On Wed 04/Mar/2020 04:00:45 +0100 Geethapriya Liyanage wrote:
In SMTP communication, normally SMTP client sends commands and SMTP
replies to that with reply codes. As in RFC 5321 , section 4.2.4,
command is not recognized, code 500 should be returned. My doubt
is, if the
SMTP server sends unrecognized command or code to SMTP client ,
will the client
also replies the same 500 code. if not, how the SMTP client should
SMTP clients can work well by just recognizing the first digit of the
code. "5", in that case, more or less means that the last command
client should stop the transaction if it's in the middle of one, and
sending without prior human intervention.
A client that cannot recognize the first digit of a reply code is not
To precisely recognize the meaning of a reply can be useful to fine
SMTP client's behavior. Interpretation of reply codes can be done by
who read the log files or the bounce messages, or by machines. The
extended (or enhanced) status codes, which some servers display
reply code and the human readable text string, can help machine
Usually, however, the fine-tuning that can result from a correct
does not affect the immediate future of the current client/server
first digit is enough to make immediate decisions.
Thank you very much for your reply.
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