The company says it's not policy to do this — yet — but they're testing locking Yahoo Mail users out of their accounts unless they turn off ad-blocking.
Many (many, many!) Yahoo Mail users actually paid for their Yahoo Mail accounts, in the form of a bundle with their cable or DSL subscriptions. Presumably you can get around this by just using a mail-client to pull your Yahoo Mail over POP or IMAP (the last time I checked, you could use Gmail to read your Yahoo Mail this way).
"At Yahoo, we are continually developing and testing new product experiences," a Yahoo rep explains. "This is a test we're running for a small number of Yahoo Mail users in the U.S."
While we understand that billions of dollars are lost each year to blocked ads, we're not sure if holding someone's e-mails hostage is the best route to go for Yahoo, especially since the company can't even get all of its own employees to use Yahoo Mail.
Use AdBlock And Yahoo May Block You From Reading Your E-Mail