> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apollodeploy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Root domain or subdomain?

> Compare the verified Signal consequences without treating a design preference as a guarantee

Signal can register a sending domain that matches your intended From-address domain.
Whether that identity is an organizational root such as `company.com` or a subdomain such as `mail.company.com` is an operational choice.

## Product facts that do not change

* Signal generates verification records for the exact domain you register.
* A From address must use a domain verified in the authenticated project.
* The domain has its own region and verification status.
* A different sending domain requires a separate registration and DNS verification.
* Tracking uses a separate project-wide tracking host when configured.

## Observable differences

| Choice      | DNS consequence                                                           | Integration consequence                                                                                 |
| ----------- | ------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------- |
| Root domain | Signal records share the root zone with other organizational mail systems | Existing employee, support, and provider senders must be considered when changing authentication policy |
| Subdomain   | Signal records live under a distinct DNS namespace                        | From addresses must use that subdomain and callers must be updated accordingly                          |

A subdomain creates a separate DNS namespace.
That is useful for ownership and change control, but Signal does not guarantee inbox placement or reputation isolation merely because a subdomain exists.

## Questions to answer before registration

1. Which From addresses will the application actually use?
2. Who controls authoritative DNS for that exact name?
3. Which existing senders already use the root or proposed subdomain?
4. Which project and region should own the domain?
5. Which tracking host will the project use?
6. Can every caller be migrated if the From domain changes later?

## Changing the choice later

Signal does not rename an existing domain registration.
Register the replacement, publish and verify its records, update controlled callers, observe delivery and webhooks, then retire the old sender only after usage stops.

<Note>
  This article describes platform consequences, not a universal deliverability rule.
  Mailbox placement depends on systems outside Signal's domain-registration choice.
</Note>