Re: [ietf-smtp] SMTP Reply code 500

[Geethapriya Liyanage <[e-mail]>]

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