Many users of the Firefox Relay service have been upset in recent days after it was included in a "disposable email service" block list.
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Firefox Relay is a privacy-focused email service, allowing users to protect their real email addresses and therefore limit spam.
The service hides the user's real email address to help protect their identity by giving them a pseudonym to use. Disposable email address services work by providing users with a temporary, intermediate email address that "forwards" mail to their real inbox.
Users who sign up for Firefox Relay are assigned an email alias @*.mozmail.com that forwards their mail to their real email.
However, disposable email services can be a headache for service providers. For example, mission-critical websites that provide e-commerce and online banking services can become vulnerable to abuse by malicious users if they allow the use of disposable emails.
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In November 2021, the Firefox Relay team lead had asked the maintainer of a list to exclude the specific domain from his block list.
“We operate Relay with a number of features that I think mitigate the risks posed by these pseudonyms,” Mozilla privacy and security engineer Luke Crouch.
First, if an @mozmail.com alias is disabled by the user, any emails sent to the alias are not bounced, but instead are rejected with a 404 error message returned by the service's HTTP webserver, Crouch said.
Second, the anti-abuse protections built into Relay limit free users to a total of five aliases and a few more to premium customers, so they can't abuse the service.
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The move to propose adding the Firefox Relay main domain to the block list of disposable email providers has caused confusion and discontent among many users, prompting the list's maintainers to lock the GitHub before things got too heated.
