Rob Pegoraro's post | Latest updates on Sulia
Yahoo finally gives up on charging for offline access to webmail--and adds un-advertised IMAP support.
Yahoo Mail turns 16 years old today (counting from Yahoo's 1997 purchase of RocketMail: http://news.cnet.com/Yahoo-buys-Four11-for-free-email/2100-1023_3-204033.html), and the company marked the occasion by revising its interface and making a bunch of premium features free (http://yahoo.tumblr.com/post/63462971435/yahoo-mails-sweet-16-is-sweet-a-brand-new-view).
The biggest one among them is free offline access. Yahoo's official blog post only cites POP downloading, but I was able to get IMAP synchronization rolling, with a hiccup or two, in Mozilla Thunderbird by letting it automatically configure the account. That's vastly more useful than POP for anybody with multiple computers.
Current Yahoo Mail Plus subscribers can keep paying $19.99 a year for ad-free service, but that will cost $49.99 annually for everybody else (http://help.yahoo.com/kb/index?locale=en_US&y=PROD&page=content&id=SLN15954).