# Allowed Domains

> Configure which email domains can sign up to your Last9 organization.

Source: https://last9.io/docs/allowed-domains/

Allowed Domains define which email domains can sign up to your Last9 organization when it is in **Open Access** mode. Based on the email ID of the first user from your organization who signed up, everyone with an email matching the same root domain is added to the same Last9 account, and that first user becomes the associated admin.

If your organization uses multiple email domains (for example after a rebrand or acquisition), admins can add additional allowed domains directly from the UI.

## Managing Allowed Domains

1. Navigate to [Settings > Allowed Domains](https://app.last9.io/settings/allowed-domains)
2. Click **Add Domain** and enter the domain (for example `acme.com`)
3. Click **Save**

Any user with an email matching an allowed domain can sign up and access the organization, provided the organization is in Open Access mode. In [Invite Only Mode](/docs/users/#invite-only-mode), only explicitly invited users can sign in regardless of domain.

:::note
Only admins can add or remove allowed domains. To change the primary root domain or the associated admin, contact [support@last9.io](mailto:support@last9.io).
:::

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## Troubleshooting

Please get in touch with us on [Discord](https://discord.com/invite/Q3p2EEucx9) or [Email](mailto:support@last9.io) if you have any questions.