[avian]

From the FAQ [1]:

> Why won’t a site accept my ⁨Relay⁩ alias? Some sites [...] have stopped accepting all addresses except those from Gmail, Hotmail or Yahoo accounts.

I think a more likely explanation is the fact that many sites these days block the usage of email addresses from domains known to host disposable addresses. For example, mozmail.com (the top domain that is used by Firefox Relay) appears on [2] that is sourced by many libraries on GitHub.

[1] https://relay.firefox.com/faq

[2] https://github.com/disposable/disposable-email-domains

[groovecoder]

We sent them a pull request to remove mozmail.com now that the aliases should be "safe"r for relying parties to accept.

upvotes maybe?

https://github.com/disposable/disposable-email-domains/pull/...

[summm]

When your business model depends on not accepting arbitrary email address, it's probably a bad business model?

[musicale]

The most popular way to defeat email based user privacy services (as provided by Apple, Firefox, etc.) is to require a phone number for "verification" or "security" purposes.

In addition to being harder to acquire in bulk, phone numbers serve as a convenient non-anonymous and universal user identification key that can be easily matched by data brokers and shared to track customers across multiple businesses.

Facebook pioneered this approach by adopting SMS-based 2FA as a means of acquiring phone numbers to match users with purchases at partner businesses.

Phone numbers also enable businesses to send unsolicited text messages and robocalls.

[kasabali]

Who said anything about business? Even random forum signups are throwing a fit when you tried to use temporary email domains.

[musicale]

I assume forums are trying to make it harder for spammers to sign up, but by doing so they are blocking users who don't want to be spammed themselves.