From Monday June 3rd, Yahoo's "classic" Mail interface is no more. Yahoo unveiled a redesign of its webmail interface late last year, but has until now allowed users to use the old version. Anyone that hasn't signed up for to the new experience will be prompted to upgrade or give up on Yahoo Mail altogether. To upgrade, you'll have to agree to a new terms of service agreement that grants Yahoo the permission to "scan and analyze all incoming and outgoing communications content sent and received from your account." The company notes that it collects and stores some data to "provide personally relevant product features and content, to match and serve targeted advertising and for spam and malware detection and abuse protection."
In exchange for giving Yahoo these extended permissions, you'll get a cleaner interface that better matches the company's mobile apps and improved navigation features. Yahoo's decision to scan and analyze its users' emails has ruffled a few feathers, but it's worth noting that the company's automated scanning policy seems to be virtually identical to the way Google targets ads in Gmail.