Yahoo Mail is reportedly testing a feature that blocks users who block ads.

Digiday first spotted(Opens in a new window) people complaining in an Adblock Plus forum thread(Opens in a new window) about Yahoo Mail being blocked on Chrome and Firefox.

Some have since found workarounds, but many are complaining on Twitter and threatening to ditch Yahoo. Even Andrei Herasimchuk, Yahoo’s former Senior Director of Product Design who helped revamp Mail, tweeted his regret over the adjustment.

So @YahooMail(Opens in a new window) has blocked my inbox for using an ad blocker. It was a good run, I guess. Goodbye! Hello Apple Mail, as much as I hate it.

— Andrei Herasimchuk (@Trenti) November 19, 2015(Opens in a new window)

But as Digiday pointed out, the practice of preventing ad-blocking users from accessing sites is becoming more popular. London’s City AM newspaper, for example, just launched such a trial(Opens in a new window). And The Washington Post has been experimenting with a similar tactic(Opens in a new window) since September.

“At Yahoo, we are continually developing and testing new product experiences,” a company spokeswoman told PCMag. “This is a test we’re running for a small number of Yahoo Mail users in the U.S.”

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For more, see PCMag’s review of Yahoo Mail.