On 13/12/2018 08:29, Benoit Panizzon wrote:
Hi List
So based on my observation I wonder...
Upon receiving a 452 4.5.3 error, what should the sending MTA do?
Reconnect immediately and re-try the soft failed recipients as would
be done with the usual 'too many recipients' situation? Or is it
correct to wait for the backoff timer?
The ONLY thing the sending MTA is required to do is to try the message
again later.
It does not have to interpret the error message beyond the initial '4'
character meaning 'try again later'.
Read RFC 5321 section 4.2.1.
https://tools.ietf.org/html/rfc5321#section-4.2.1
Even if a sender does interpret more characters, then according to RFC
5321, the 452 response code means (section 4.2.2):
452 Requested action not taken: insufficient system storage
So, an immediate retry is probably not warranted by that response code.
The 4.5.3 extended status code may give more information, but there's no
need for an email sender to even know that those extended status codes
exist. Note that according to the IANA
(https://www.iana.org/assignments/smtp-enhanced-status-codes/smtp-enhanced-status-codes.xhtml)
, the 4.5.3 should be preceded by 451, not 452 (SMTP defines 451 as
'Requested action aborted; error in processing')
--
Paul Smith Computer Services
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