email popup keeps asking me for my ID and password when I enter it it pops up again and again and I

Are you using an email client app (e.g., Thunderbird, Outlook, mobile email client apps, etc.) or the webmail?  If a client, which one?  And if a client use a secure mail key in place of the password in that client.  Read this (which includes a link to how to create a secure mail key).

Also do you have a legacy account (e.g. sbcglobal.net, pacbell.net, bellsouth.net, etc., i.e., any att account other than ending with att.net)?

The same thing is happening to me. The popup is driving me crazy.  I do have a legacy account (@sbcglobal.net) so what are you suggesting in my case?

If you are using an email client app (OP never bothered to answer my questions so all I can do is guess here) and you answer the password prompts does it work?  If yes then I think the problem is with your client.  If not using an email client don't bother reading further.  I don't know why you are getting repeated prompts from the webmail. 

Email clients need the password whenever they need to access the POP/IMAP/SMTP servers, e.g. when receiving, sending, syncing with the server, whatever.  If they don't have the password or it's wrong they will usually ask for the proper password whenever they need it.  If there is no option in the prompt to tell the client to remember, or you don't set it if there is, it's going to prompt every time.  I suspect it is happening in the first place because the password setting is wrong in the client.  You should set it properly.  This is why I asked if the password you are using to answer those prompts is working.

I'm using Outlook, and when I enter my password in the popup, it does NOT work, and the popup comes up again and again.

Oh I may have misinterpreted the problem.  I thought the problem was the prompt comes up, you give it the correct info which is accepted, email client does it's task until it needs the password again.  If it never accepts the password then try logging into the webmail.  If you can't even log in there then don't expect an email client to do any better.  All I can suggest then is to try to change your password.  Sometimes that works for some users.

Also, I find conflicting info on what the servers should be for sbcglobal.net. I've tried all variations. What should they be?

There are only two sets of choices.  The att server settings or the yahoo server settings.  Given you have an att legacy account I would stick with the att/yahoo settings.

I had the same problem for 24 hours. I just got it fixed. You have to call ATT for the  PW reset.  1-800-288-2020   1st prompt say  "Password Reset" then wait for the next prompt and say "AGENT" repeatedly to the automated system so that you will be routed to a live specialist. At that point they can help... Took me 10 min.... Im also on sbcglobal.net