Antispam validation failed for your domain in Accounts.That means the sending provider rejected the domain during its anti-spam check. DNS records will not appear. You cannot finish custom domain setup until this is cleared.
What to send support
Email [email protected] with the domain you tried to add. The domain only is enough. Until support clears it:- Leave the default sender in place.
- Do not keep retrying the same domain.
- Alerts still send from
[email protected].
Shopify development stores cannot register a custom domain. That is a different limit, not DE_150.