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.
Yahoo joins a growing list of websites fighting back against ad block software as they depend on revenue from advertisements to finance their operations.
Internet users attempting to acess the Washington Post's website while using the software in September discovered that they were barred from viewing the site and redirected to a subscription page or told to enter their email address to unlock the article they wanted to read.
You might be asking “if I’m not subscribed, then why is there an unsubscribe link? The act of clicking that “unsubscribe” link actually confirms to the spammer that your email address is a real, valid email address with a real person reading it.