E05011 — DomainHostnameReserved

This hostname is already in use as a return-path or tracking domain. Remove that configuration first, or choose a different domain.

• HTTP status: 409
• Type: conflict_error
• Name: DomainHostnameReserved

What to do

Remove the return-path or tracking configuration that uses this hostname, or choose a different domain, then retry.

Operations that resolve this:

• List sending domains
• Update a sending domain

Related

• Idempotency: safe retries and key reuse rules
• E05xxx — Domains & DNS: every code in this range
• Errors: the full wire contract, status mapping, and error catalog
• Error handling: branching on type and code, validation details, and vendor_code