[JoshTriplett]

That's a service that doesn't want your business. If you care, message them about it

I've never once run into a service with such a restriction, but I can imagine someone being that short-sighted. I have seen services that only support "log in with Google or Facebook", which is comparably terrible.

[genxy]

Discogs will not let me login with my own domain (of 30 years) and required one of the big providers. It kept complaining about "risky domain". But that is the only incident I can think of.

[CamperBob2]

Discogs

Who? Never heard of them, and it sounds like there's a good reason for that.

[sir0010010]

I've run into services that will flag specific tlds as invalid.

[JoshTriplett]

I have heard of that, yeah. It's still busted, but marginally more understandable if they're dealing with a lot of scams. For instance, `.xyz` and some others have bad reputations. I've never seen something that'll reject an arbitrary self-owned `.org`, by way of example.