Well if AT&T is just now telling you about the Yahoo breach that are pretty slow. But yes the process is still the same, reset your password for your email account as well as any service that shares the same password.
If you're looking for an alternative email service, there are several good...
You need to change your password for that service. In addition, you also need to change the password at any other service that you use that shares the same password - if you re-use passwords which I hope you don't.
Also are you sure this is a legit email? I haven't seen any news about an AT&T...
If your haven't reset your yahoo password since around that time then you'd be best to at the very least change it now. This data breach is now making its rounds around the internet.
You are partly right about other providers. Some can provide the info requested for individual users. This is...
In case you've missed the announcement about Yahoo losing 500 MILLION user account passwords, email address, phone number and security questions or that fact they knew about it when it happened TWO years ago and said nothing or did nothing (like force a password reset).
It's now known that...