Pacbell.net email stops working on all of my Apple products.

My Pacbell.net email stopped working on all my macs and iphones. They of course are part of ATT these days but before that Yahoo. Email login works correctly on the browser client. So i tried recreating the accounts using "other" no luck. I'm seeing on the net that i may have to use a "Secure Key" or something like that. could really use some help on this one. All other info seemed to be outdated.