May 7, 2026
3:31 p.m.
Stephen Daniel writes
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 XXX.org with ip X.Y.Z.W = SUCCESS. See https://senders.yahooinc.com/smtp-error-codes/#authentication-failures for more information. This has worked for a long time. What would suddenly cause DKIM failures?
I just saw the same thing with all my yahoo subscribers. Yahoo are the worst freemail provider I have come across.
I contacted all my yahoo subscribers. They gave me non-yahoo addresses.
-- Written by Thomas Krichel http://openlib.org/home/krichel on his 22252nd day.