ATT E-mail Problems

I run an iMac. My Internet provider is ATT U-Verse (they use Yahoo.com for their e-mail system). This AM, I got a message that my system couldn't log into my att.net (yahoo) e-mail account, wrong password. Curious thing, my iPad and iPhone still get my ATT mail. I spent an hour on the phone with ATT, the 2nd level "Support person" tried selling me a $15 month service plan so they could "help" me. I refused. Called Apple Care. They have info that ATT is changing servers and protocols. This is an "intermittent e-mail problem".... I have yet to call ATT back... considering canceling my service. Have others recently had this type of problem?