After Twitter user Jason Kint pointed out the change, Oath confirmed the practice to CNET.
The policy states that Oath "analyzes and stores all communications content, including email content from incoming and outgoing mail." It also points out that it scans attachments, including the EXIF data for photos and videos, as well as any information sent to you by your bank.
While Yahoo mail was already being scanned, AOL was not. And while it's easy to say people should just jump ship (it is 2018, after all), some people have built their digital lives around these addresses.
You can, to a point, opt out. Yahoo users can go here to opt out of targeted advertising, though it's less clear what AOL users can do.
Google's Gmail may be an alternative for some. While Google does scan your inbox to use its data throughout its services (an appointment made in Gmail can end up in Google Calendar, for instance), it stopped reading emails to deliver targeted ads in 2017.
Verizon acquired Yahoo last year for $4.5 billion, which it merged with its ownership in AOL to create Oath. Other Oath properties include TechCrunch, Engadget, Tumblr, MovieFone and HuffPost.