Additional security features in Yahoo Mail
As part of Yahoo commitment to user safety, we've introduced a series of alert messages that will appear if we think you're in danger of your account having been compromised. One of the ways we do this is by letting you know if you've set up a Reply-to address, or enable Mail Forwarding. While these features are used legitimately by Yahoo customers every day, they are often also exploited by scammers wanting to cause you harm.
If we detect that the email address you'll receive replies to is other than the one you're sending the message from, we'll let you know with a little alert on the top of the message. If you've set up the reply-to function in your email, then there's no worries! But if you didn't set that up, you should secure your account immediately.
When you log into your account after Mail Forwarding has been set up, you'll get an alert notifying you that auto-forwarding has been set up. If you enable it, there is nothing that needs to be done.
If you did not set this up, click or tap on "Disable Forwarding" and follow the prompts to disable it and change your password.