I had the same problem with my Yahoo e-mail last week, and no matter what I did, no luck. I waited a couple of days and tried again, and now it is back to working again. I have no idea what the problem is or was. I have two Yahoo e-mail accounts and could only access one of them from from my iMac and Mac mini. Bizarre!?! I tried changing the password on the one that I could access, but that made no difference. Still couldn't access the other account. Sorry I couldn't be more helpful.