I have received several emails about signing onto Oath’s terms of service & AT&T states in the same email that nothing will change for AT&T. Do I sign onto the terms of service in the email I received?
I wouldn't. I haven't heard of anyone actually getting emails about this so that might be phishing. It usually comes in the form of a browser popup giving you a chance to accept, do it later, or dismiss the popup. If you read the OATH TOS you might not ever want to accept anyhow (see this, particularly the section "Information You Provide to Us").
But it's all academic anyhow now. You have already accepted their TOS by now simply by continuing to use the yahoo servers (through webmail or an email client app).
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