We are very sorry for recent difficulties with Yahoo Mail.
Some of our users have not been able to access their mail since 10:27 PM PT on Monday night, due to a hardware problem in one of our mail data centers. The issue has been harder to fix than we originally expected.
We have dozens of people working around the clock to bring it to a resolution. We believe our current efforts will restore our users’ access to their inboxes by 3 pm PT today. We’ll post again then on our @YahooMail Twitter handle.
by Jeffrey Bonforte, SVP of Communication Products
Kara Swisher has reported that Bonforte acknowledged complaints, but said users will suck it up and stick around. In other words, Yahoo is a bit cocky and doesn't think complaints will matter in an actual revolt.
It's time to prove them wrong and move to another email service. Gmail and Outlook.com are fine alternatives.