Not too much help here but... https://www.iana.org/assignments/smtp-enhanced-status-codes/smtp-enhanced-status-codes.xhtml
X.7.0 Other or undefined security status Associated basic status code: 220, 235, 450, 454, 500, 501, 503, 504, 530, 535, 550 "Something related to security caused the message to be returned, and the problem cannot be well expressed with any of the other provided detail codes. This status code may also be used when the condition cannot be further described because of security policies in force." A simple google search gives you an answer from yahoo though, given that the part of the defer message you omitted was "Messages from x.x.x.x temporarily deferred due to user complaints": https://forums.yahoo.net/t5/Delivery-errors-5xx-and-421/421-4-7-0-TSS04-Messages-from-lt-IP-gt-temporarily-deferred-due/m-p/557541/highlight/true#M5737 BR/Mvh. Dan Malm, Systems Engineer, One.com On 2018-11-07 11:19, Mathieu Marnat via mailop wrote: > Hi folks, > > > On some of our IPs we get a lot of 421 4.7.0 [TSS04] SMTP responses from > Yahoo. > > I cannot get a clear explanation from them and I see that this error code is > not listed in their official SMTP error code table. > > It seems to be a newly implemented error code and since they already had > error codes about complaints or unusual traffic what does this one could mean > ? More details would be helpful. > > > Regards, > > > Mathieu. > > > _______________________________________________ > mailop mailing list > mailop@mailop.org > https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop >
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