On Thu, Aug 21, 2025 at 7:06 AM Russell Clemings via mailop < mailop@mailop.org> wrote:
> 550 5.7.9 This mail has been blocked because the sender is > unauthenticated. Yahoo requires all senders to authenticate with either SPF > or DKIM. Authentication results: DKIM = FAILURE - SPF xxxx.xxx with ip > 209.85.214.178 = FAILURE. See > https://senders.yahooinc.com/smtp-error-codes/#authentication-failures > for more information. > > It looks to me as if Yahoo is expecting the "from" field to pass SPF > instead of (or in addition to) the envelope sender. Or is there a different > issue that I'm not seeing? > > You could follow the link in the SMTP message... It seems your users are sending emails via their Google consumer accounts with domains in the "from" field, which are not properly set up to send via Google's servers. We require SPF or DKIM and we require either SPF or DKIM to align. Solution is to sign with an aligned DKIM domain. -- Marcel
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