I've encountered more than a few places that block temp emails like 10minutemail etc. It's so infuriating.

They have yet to block the Apple email relay. Granted, I haven't used it or tested it on every site. That said, Apple has one advantage other filters don't have, which is people who own Apple devices tend to be desirable to very desirable customers, which means adding friction to this would drive away higher average spenders.

I also use the fastmail.com masked email address for things, and that has not yet been an issue either.

Same. Pretty sure Meta was the first to get mad at me for it.