On 2/24/2023, Christine Borgia via mailop wrote:
It is transient, but they are blocks and are not retried. Weird, right?
I have an opinion on this;
This appears to be a specially built MTA, and with the (probable)
consent of its users, has policy in place to not resend after 4xx under
specific conditions. I.e. the sending MTA is interpreting specific 4xx
responses (and more likely the text) to mean a permanent failure.
I do not see a problem with elevating a 4xx to mean 5xx where the users
of the system understand the policy as it does not appear to impact the
receiving system. In fact one could take section 4.5.4.1 of RFC5321 to
opening the door for just that; "[...] however, more sophisticated and
variable strategies will be beneficial when the SMTP client can
determine the reason for non-delivery."
I do have issues where that 5xx is treated as a 4xx (with the exception
of the correction to the minimum/maximum problem, first pointed out in
RFC2821. See RFC5321 section 4.5.3.1.10) as this has an impact on the
receiving system.
--
Denny Watson
Lead Investigator
The Spamhaus Project
_______________________________________________
mailop mailing list
mailop@mailop.org
https://list.mailop.org/listinfo/mailop
