Why am I getting Yahoo login when my e-mail account is att.net?

My wife and I are flustered that when we want to sign in to our att.net e-mail we get a Yahoo login screen. If we are at&t customers we expect an at&t login screen! Also we have recently been getting a pop-up message from some other outfit that says something like "We are 'Oath', we have joined with Verizon and Yahoo,(and a few other companies), we are upgrading the terms of service and privacy policy. What the heck is going on here??? Months ago we were advised by computer gurus to cancel our Yahoo mail accounts for security reasons.

Now, I have at&t mail not Verizon or Yahoo or any other for that matter and I am certainly not going to agree to some other companies' 'Terms of Service' or 'Privacy Policy. With all of the insecurities and scamming going on in today's digital world we are told to beware of hackers, fishing, fraud, identity theft, fake e-mails, fake news, etc. etc. etc. We chose at&t for our internet service and e-mail because we thought a long established and trusted company would be the safest one to be with. But the whole system now days seems to be very poorly integrated. All the different departments like Home, Business, E-mail, Mobile, Internet, Home phone etc. have no idea what the other is doing. The whole system seems to be more and more cumbersome and user unfriendly. And it is also very unsettling to think that big companies like at&t are reaching out to upstart companies to provide crucial services of whom we know nothing about until we get a pop-up screen that says we must agree to their new policies! Can someone fix this mess and get us a at&t only login page?

If I sign up for a vacation cruise with Royal Caribbean because they have a awesome

reputation, I surely won't have a warm and fuzzy feeling if they tell me the boat is

from Royal Caribbean but the crew is from 'Toms Tug Boat Services' and that the

chefs are from Joe's Diner.I think I have made myself clear enough.

Now can someone give me some reassurance?!

If I sign up for a vacation cruise with Royal Caribbean because they have a awesome

reputation, I surely won't have a warm and fuzzy feeling if they tell me the boat is

from Royal Caribbean but the crew is from 'Toms Tug Boat Services' and that the

chefs are from Joe's Diner.

 I think I have made myself clear enough, but I still am not sure that anyone in at&t will

even read this since I am on some kind of forum.