I have used the same email address on Yahoo since I got a computer 20 years ago. Now there seems to be an authentication issue that Yahoo has changed and I can no longer use that email address for a lot of things it is either rejected is invalid or I can't send emails to other people from my Yahoo address. I don't want to change email addresses after so many years but how can I get it authenticated to use on things and also have it be allowed to send a text message to other people?
Thanks for providing the details of the non deliverable email "554 5.7.9". Your Yahoo email account has been flagged as potentially sending spam, it's possible the account was compromised so change your password first and stop sending email for at least 24 hours ( the lockout may clear automatically). While you are waiting verify the imap settings are correct on your phone and desktop.
How does that help? I updated my mail account earlier this year to the new mail. My last message was not sent and I was unable to use my email to receive information bbcause of a new protocol for yahoo, but there is nothing I can find that fixes the verification/ validation error message.
It gives you two options. Ask the Yahoo community, and look at all our help articles. There is no help article that I can find Regarding the changes in Yahoo mail that regard things being sent from a Yahoo account as spam or fraudulent. This is just happened in the last few days I believe but this is my email address and I literally have 20 years worth of email I do not want to try and change it now. There should be some sort of fix or workaround to make these Yahoo accounts validated or verifiable. I have posted in the Yahoo help community but I posted here because people are generally very knowledgeable
I requested information from a company using my standard yahoo email. When I click submit, it says Your email appears to be invalid. Please check it and try again! . It did it numerous times. Then I tried to send an email from my yahoo address to a yahoo address with a short video attachement and I got an error message Error: "554 5.7.9: Message not accepted for policy reasons" when sending email to Yahoo. It also said Your message wasn't delivered because Yahoo was unable to verify that it came from a legitimate email sender.
Your email failed one or more authentication checks that Yahoo uses to verify emails are truly sent from the domains they claim to originate from. I can only find information about business issues and that you should contact your domain host or administrator. There is nothing I can find about personal accounts.