If emails got into spam on Yahoo, you will see information about this in the error details.
Yahoo - a foreign service, all blacklist decisions are made completely automatically.
Therefore, if your emails got into spam, the only way out is not to send any emails and notifications to @yahoo.com for 4 days. After that, the blacklist will be reset, and you will get out of spam.
The second option, which we can recommend, is not to send any emails to Yahoo at all, only if the user with such a mailbox did not register on his own, while confirming his email address.
You can learn more about what rules Yahoo sets for receiving mail from the user agreement.
We also recommend a detailed article on what factors affect the email deliverability.
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