Yahoo has already announced back in April that it will shut down its email service in China. After 4 months of closure announcement, Yahoo email service is now closed today for Chinese users. Sunday, August 19th was the last day to migrate accounts on alternative services.
Yahoo China has a strategic partnership with local Chinese e-commerce giant Alibaba to run its services in the country. Alibaba is offering all Chinese Yahoo Mail users to transfer their accounts to its own Aliyun email service called 'Alimail' that offers Ali cloud mailbox. The switched users will get an extra advantage for this. They can forward their emails through their old Yahoo Mail accounts till December 31, 2013.
Yahoo email users have other alternative options like QQ Mail by Tencent or 163 Mail by Netease. But these will not give forward messaging advantage. Yet both of these email services have their iOS apps for Apple devices.