Apple’s plan to change a privacy feature that lets paying customers hide their real email addresses when creating online accounts could make it easier for apps and websites to block anonymous sign-ups.

Apple’s Hide My Email is an iCloud+ feature that generates anonymous email addresses under the @icloud.com domain, which then forward messages to a person’s real email address. The reason these privately generated email addresses work is because they cannot be distinguished from regular Apple users, whose email addresses also use the @icloud.com domain.

Apple said in a note to developers on Monday that in the coming weeks the company will move its anonymously generated email addresses to @private.icloud.com, effectively making it easier for apps and websites to know that an email address is private and block users from signing up.

Existing addresses will continue to function and forward mail without interruption, Apple said in the note to developers. The company added that app and email providers would have to update their filtering to ensure that emails to customers who rely on the feature continue to go through.

Several Apple users on Reddit criticized the change to the email domain, saying it would make it more difficult to use the service. 

Apple did not respond to a request for comment from TechCrunch about the change, or explain why it made the change.

Earlier this year, TechCrunch reported that Apple turned over the real account information of a user who generated an anonymized email address using Hide My Email to send an allegedly threatening email to the girlfriend of the FBI director Kash Patel.

The Trump administration has made efforts over the past year to unmask anonymous accounts, including those of Trump’s critics, by using subpoenas to demand that tech companies turn over information about their users.