I’ve confirmed this is no longer the case by registering a new account under a newly registered domain name (from WHOISDS 10/15/23) although I’ll never be able to confirm the email because it wasn’t my domain, but it did allow registration with the email and did not give the “try a new email” message.
This seems to be an ongoing problem at times, but when I tried I had registered my domain with Cloudflare over 24 hours before and the correct DNS including MX/DKIM/etc had been propagated worldwide (confirmed by dnschecker.org) and still got the “try a different email” error from Etsy when attempting to create a new account from a residential IP address.
But I’ve confirmed you are correct, it sometimes has no issues and other times it does. The rest of them I also don’t know currently, but in the past had that issue.
I’ve confirmed this is no longer the case by registering a new account under a newly registered domain name (from WHOISDS 10/15/23) although I’ll never be able to confirm the email because it wasn’t my domain, but it did allow registration with the email and did not give the “try a new email” message.
This seems to be an ongoing problem at times, but when I tried I had registered my domain with Cloudflare over 24 hours before and the correct DNS including MX/DKIM/etc had been propagated worldwide (confirmed by dnschecker.org) and still got the “try a different email” error from Etsy when attempting to create a new account from a residential IP address.
I’m not alone: https://duckduckgo.com/?q=etsy+custom+domain+name+cant+register+site:reddit.com&ia=web
But I’ve confirmed you are correct, it sometimes has no issues and other times it does. The rest of them I also don’t know currently, but in the past had that issue.
Edit: fixed DDG URL