First check the time and date are correct on the pc or laptop.

OK, those are correct.

I don't have an answer other then try a reboot , others may chime in.

Yeah, I've done that already. What's weird is that when I was on the phone with AT&T (my provider) every time I tried to sign into their website - on three different browsers - I got locked up and when I went to other websites it didn't. The only other thing different was that this morning there was a notice from Norton that I needed to reboot my machine because they had done a live update - so I did. Could that be it?

But thanks for trying.

I suppose it could be Norton and it's always fun to blame everything on Norton.

Can you open Norton and perhaps disable anything to do with mail. I'll Google the error code and include the word Norton and see if anything different comes up on a search, Always search the error code although in this case not finding much, a system restore is a thought also.

Since AT&T uses Yahoo I Googled Yahoo security certificate problems and found a lot of instances of it. Answers not very clear but then I'm not tech savvy anyway. I might have to reset all the parameters and see if that works. I'm going to hold off and see if they might have changed something on their end and are deluged with enough complaints to remedy it before I do. I have a sneaky feeling the guy I talked to yesterday either wasn't well informed or was dodging the issue.

Yes. I would agree.

Welllll now - I think my hunch was right. All of a sudden the problem has cleared up and it's not anything me or Norton did because they haven't done anything since before I had this problem. I guess the AT&T guy was either uninformed or blowing smoke. I'm feeling that is was something yahoo did and rectified it today.

The server's security certificate had expired, it's a maintenance or licensing issue on the mail server side. I kind of makes me mad that AT&T tried to blame your computer software. Rarely would a security certificate error be on the computer side of things.

Just goes to show that the bigger the organization is the worse the customer care. I am very angry that the real problem was not addressed when I was talking with AT&T. I tried to find an email address to voice my opinion and there isn't one to be found at AT&T's website and the maze you have to go through on the phone is ridiculous. If I hadn't thought of Googling the problem by including the search term "Yahoo" I would still be in the dark about it. And not a word has been issued on the news about the problem and there had to be millions affected by it.

Server security certificates expire on a regular/recurring basis, typically yearly. Not unusual that whoever is supposed to keep track of it slips-up and misses a renewal until after-the-fact, although of course that shouldn't happen.