# Restrict user email addresses to certain domains

{!admin-only.md!}

Zulip allows organization administrators to block new users from signing up
who are not in their organization. The administrator can accomplish this by
restricting users to have email addresses only from the organization's
domains.

{!go-to-the.md!} [Organization permissions](/#organization/organization-permissions)
{!admin.md!}

2. Restricting user email addresses to certain domains can be enabled or disabled
 with the **Users restricted to (allowed domains)** checkbox in the
 **Joining the organization** section.

    !!! tip ""
        The allowed domains will be listed after the **Users restricted to**
         next to the checkbox.

3. Domains can be added to the allowed domains list by clicking on the **Change domains**
link next to the checkbox to reveal the **Allowed domains** list. You
can then add a domain to the list by typing the domain into the box underneath
the list and clicking the **Add** button.

    !!! tip ""
        Domains can be deleted from the **Allowed domains** list by clicking the
        **Delete** button next to a domain on the list. However, you must have
        at least one allowed domain if the **Users restricted to** option is
        enabled.

5. Once you have made all your changes, exit out of the **Allowed domains** list
 by clicking the x (<i class="icon-vector-remove"></i>) icon in the top
 right-hand corner of the **Allowed Domains** list.

{!save-changes.md!} organization settings.
