I received an email that at & t was moving to yahoo..I clicked on it and now can not get emails?

I received an email from at & t yesterday that they were moving their mail to yahoo. Now whenever I try to go into at & t email it automatically sends me to yahoo, but I am not getting any emails at yahoo. I tried to send myself an email at my bel-south address, but it never goes to yahoo and won't let me into bell-south anymore..HELP