On Thu, Feb 1, 2024 at 1:01 PM Robert L Mathews via mailop < mailop@mailop.org> wrote:
> I see occasional bounces from AOL/Yahoo that look like this: > > 554 5.7.9 Message not accepted for policy reasons. See > https://postmaster.yahooinc.com/error-codes > > However, the "554 5.7.9" doesn't make sense to me. > > The "554" part is "Transaction failed" (RFC 5321), which is fair enough > (although unhelpfully vague, as is "policy reasons"), but "5.7.9", > according to RFC 4954, is: > > >Authentication mechanism is too weak > >This response to the AUTH command indicates that the selected > >authentication mechanism is weaker than server policy permits for > >that user. The client SHOULD retry with a new authentication > >mechanism. > > This is in response to an SMTP end-of-DATA command, though, not an AUTH > command. No other company appears to send "5.7.9" as part of an enhanced > SMTP response. > > Am I misreading the RFCs? What is AOL/Yahoo actually trying to indicate > here? (And have other people started seeing more of these errors recently?) > I've seen as yet unconfirmed speculation that this might be the error response Yahoo is using for those that don't comply with the new (as of today) requirements that mail be authenticated using SPF, DKIM, and DMARC. See also - https://senders.yahooinc.com/best-practices/ -- *Todd Herr * | Technical Director, Standards & Ecosystem *e:* todd.h...@valimail.com *p:* 703-220-4153 *m:* 703.220.4153 This email and all data transmitted with it contains confidential and/or proprietary information intended solely for the use of individual(s) authorized to receive it. If you are not an intended and authorized recipient you are hereby notified of any use, disclosure, copying or distribution of the information included in this transmission is prohibited and may be unlawful. Please immediately notify the sender by replying to this email and then delete it from your system.
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