Yahoo Mail is not looking kindly on some users of ad-blocking software. A thread on the forums for the service Adblock Plus, first spotted by Digiday, suggested some Yahoo Mail users were being prevented from accessing their email unless they disabled their ad blockers, and a Yahoo spokesperson confirmed to The Verge that the message is indeed part of a "test" for some users.

"At Yahoo, we are continually developing and testing new product experiences," the spokesperson said. "This is a test we're running for a small number of Yahoo Mail users in the U.S." According to the forum posts, when users attempt to access Yahoo Mail, they're instead greeted by an error message: "Uh oh... We are unable to display Yahoo Mail. Please disable Ad Blocker to continue using Yahoo Mail."

Although Yahoo is hardly the first to experiment with detecting ad-blocking software and then prompting users to disable it — many news sites, for example, have taken that action — it's more rare that a critical service like email is put behind such a wall.