Dear Yahoo,

I have been using yahoo for over 20+ years, and would love to keep it, but recently my forwarded letters from Gmail are not always working. I receive an error from yahoo side when try to forward my gmail messages. Those letters are coming from secured sources, and still have the following error.
How can I solve this? Of course, I cannot contact the original senders (who sent mails to my gmail account).

Many thanks
Balazs
Error message:

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 onlinetoner.hu with ip 209.85.222.49 = FAILURE. See https://senders.yahooinc.com/smtp-error-codes/#authentication-failures for more information.

Final-Recipient: rfc822; heltay86@yahoo.co.uk
Action: failed
Status: 5.7.9
Remote-MTA: dns; mx-eu.mail.am0.yahoodns.net. (188.125.72.74, the server for
the domain yahoo.co.uk.)
Diagnostic-Code: smtp; 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 onlinetoner.hu with ip 209.85.222.49 = FAILURE. See https://senders.yahooinc.com/smtp-error-codes/#authentication-failures for more information.
Last-Attempt-Date: Tue, 20 Jan 2026 04:00:26 -0800 (PST)