> For the complete documentation index, see [llms.txt](https://docs.emaildelivery.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.emaildelivery.com/docs/common-email-setup-issues/unconfigured-sending-domain-during-test-message.md).
# "Unconfigured sending domain" during test message
{% hint style="info" %}
**Your sending domain must match the authenticated domain in your ESP account perfectly, including any subdomain.**
{% endhint %}