It's rare though.

I have been using alias services like Anonaddy and SimpleLogin for nearly two years. I have seen only on website block SimpleLogin, and it was a Pixelfed instance. I simply signed up on another Pixelfed instance as these are federated.

These alias companies also have multiple domains, so in a way these blocks can be worked around.

Mailinator's domains are pretty much all blocked in lots of cases. There are lists filled with such domains that services often seem to use.

Mailinator is very famous. I never heard about the other services in this sub thread though. It could be that they are allowed because few people know that they exist.

About a year after Gmail launched, commercial services blocked the domain for account registration, in droves. I remember seeing errors about using "free" email services. It hasn't happened yet me in a long time but I also use a wildcard address and a personal domain for most things now. (My gmail account is regularly blocked but that's becaue people assume it's fake and they use it for testing... I get all the spam.)

Some probably will.

I've find a good amount of sites that do not blacklist, but whitelist maybe four or five domains (gmail, hotmail, outlook...) and any others not allowed.

Cat v Mouse