diff --git a/doc/user/project/issues/index.md b/doc/user/project/issues/index.md
index 5f13e419332c7c8ab02d68d935bcf7d45126fd07..fd74988e668ca7d79889911f1f0cdfc7cf056b50 100644
--- a/doc/user/project/issues/index.md
+++ b/doc/user/project/issues/index.md
@@ -62,3 +62,4 @@ To learn how the GitLab Strategic Marketing department uses GitLab issues with [
- [Issues API](../../../api/issues.md)
- [Configure an external issue tracker](../../../integration/external-issue-tracker.md)
- [Tasks](../../tasks.md)
+- [External participants](../service_desk/external_participants.md)
diff --git a/doc/user/project/service_desk/external_participants.md b/doc/user/project/service_desk/external_participants.md
new file mode 100644
index 0000000000000000000000000000000000000000..82da367cee7a4e5d5f808684b92c5af289de92cc
--- /dev/null
+++ b/doc/user/project/service_desk/external_participants.md
@@ -0,0 +1,159 @@
+---
+stage: Service Management
+group: Respond
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://handbook.gitlab.com/handbook/product/ux/technical-writing/#assignments
+---
+
+# External participants
+
+DETAILS:
+**Tier:** Free, Premium, Ultimate
+**Offering:** GitLab.com, Self-managed
+
+> - [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/3758) in GitLab 17.0 [with a flag](../../../administration/feature_flags.md) named `issue_email_participants`. Disabled by default.
+
+FLAG:
+The availability of this feature is controlled by a feature flag.
+For more information, see the history.
+This feature is available for testing, but not ready for production use.
+
+External participants are users without a GitLab account that can interact with an issue or Service Desk ticket only by email.
+They get notified of public comments on an issue or ticket by [Service Desk emails](configure.md#customize-emails-sent-to-the-requester).
+
+The maximum number of external participants on an issue or ticket is 10.
+
+## Service Desk tickets
+
+GitLab adds the external author of a Service Desk ticket as an external participant.
+That usually is the email address from the `From` header of the initial email that created the ticket.
+
+### Add external participants from the `Cc` header
+
+By default GitLab only adds the sender of the email that creates the Service Desk ticket as an external participant.
+
+You can configure GitLab to also add all email addresses from the `Cc` header to the Service Desk ticket.
+This works for the initial email and all replies to the [`thank_you` email](configure.md#customize-emails-sent-to-the-requester).
+
+Prerequisites:
+
+- You must have at least the Maintainer role for the project.
+
+To enable the setting for the project:
+
+1. On the left sidebar, select **Search or go to** and find your project.
+1. Select **Settings > General**.
+1. Expand **Service Desk**.
+1. Select **Add external participants from the `Cc` header**.
+1. Select **Save changes**.
+
+## As an external participant
+
+An external participant receives a notification for each public comment on the issue or ticket
+using [Service Desk emails](configure.md#customize-emails-sent-to-the-requester).
+
+### Replying to notification emails
+
+An external participant can [reply to the received notification email](../../../administration/reply_by_email.md#you-reply-to-the-notification-email).
+It creates a new comment on the issue or ticket and displays the email address of the external participant
+instead of a GitLab username. The email address is followed by `(external participant)`.
+
+
+
+### Unsubscribing from notification emails
+
+External participants can use the unsubscribe link in the default Service Desk email template to
+unsubscribe from the issue or ticket.
+
+If you [customize your `thank_you` and `new_note` email templates](configure.md#customize-emails-sent-to-the-requester),
+you can use the `%{UNSUBSCRIBE_URL}` placeholder to add the unsubscribe link to the templates.
+
+Your GitLab instance must be reachable (for example, from the public internet) for the external participant to successfully unsubscribe.
+If that's not the case, consider removing the unsubscribe link from your template.
+
+## As a GitLab user
+
+To see the email address of an external participant you must have at least the Reporter role for the project.
+
+The external participant's email address is obfuscated if both these conditions are true:
+
+- You are not a member of the project or have the Guest role.
+- The issue or ticket is public ([non-confidential](../issues/confidential_issues.md#confidential-issues)).
+
+The external participant's email address is then obfuscated in:
+
+- The author field of a Service Desk ticket.
+- All [system notes](../system_notes.md) that mention an external participant.
+- The [REST](../../../api/notes.md) and [GraphQL](../../../api/graphql/index.md) APIs.
+- The warning message below the comment editor.
+
+For example:
+
+
+
+### Notifications sent to external participants
+
+External participants get notifications for all public comments on an issue.
+For private communication, use [internal notes](../../discussions/index.md#add-an-internal-note).
+
+External participants don't receive notifications for any other issue or ticket event.
+
+### View all external participants
+
+Get an overview of all external participants that receive a Service Desk email for a new comment.
+
+Prerequisites:
+
+- You must have at least the Reporter role for the project.
+
+To see a list of all external participants:
+
+1. Go to the issue or ticket.
+1. Scroll down to the comment editor.
+1. If the issue or ticket has external participants, you can see a warning under the comment editor
+ that lists all external participants.
+
+
+
+### Add an external participant
+
+Add an external participant using the `/invite_email` [quick action](../quick_actions.md) when you want
+to include them in the conversation at any time.
+
+When added, the external participant starts receiving notifications using Service Desk emails.
+GitLab doesn't send a `thank_you` email for manually added external participants.
+
+You should add external participants in a dedicated comment because they don't receive a notification
+email for the comment that contains the `/invite_email` quick action.
+
+Prerequisites:
+
+- You must have at least the Reporter role for the project.
+
+To add an external participant to an issue or ticket:
+
+1. Go to the issue or ticket.
+1. Add a comment that contains only the quick action `/invite_email user@example.com`.
+ You can chain up to 6 email addresses. For example `/invite_email user@example.com user2@example.com`
+
+You should see a success message and a new system note with the email address.
+
+### Remove an external participant
+
+Remove an external participant from an issue or Service Desk ticket using the `/remove_email`
+[quick action](../quick_actions.md) when they should stop receiving notifications.
+
+After removing them from the issue or ticket they don't receive new notifications.
+But they can still reply to emails they received before and create a new comment on the issue or ticket.
+
+Prerequisites:
+
+- You must have at least the Reporter role for the project.
+- There must be at least one external participant on the issue or ticket.
+
+To remove an existing external participant from an issue or ticket:
+
+1. Go to the issue or ticket.
+1. Add a comment that contains only the quick action `/remove_email user@example.com`.
+ You can chain up to 6 email addresses. For example `/remove_email user@example.com user2@example.com`
+
+You should see a success message and a new system note with the email address.
diff --git a/doc/user/project/service_desk/img/service_desk_external_participants_comment_editor_warning_v17_0.png b/doc/user/project/service_desk/img/service_desk_external_participants_comment_editor_warning_v17_0.png
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diff --git a/doc/user/project/service_desk/img/service_desk_external_participants_email_obfuscation_v17_0.png b/doc/user/project/service_desk/img/service_desk_external_participants_email_obfuscation_v17_0.png
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diff --git a/doc/user/project/service_desk/index.md b/doc/user/project/service_desk/index.md
index 27e3817ba5a34f83b13721451122cb92d0d1047a..6dc1a67aabc567aa7b6c54f5614c58680d2c3d3c 100644
--- a/doc/user/project/service_desk/index.md
+++ b/doc/user/project/service_desk/index.md
@@ -64,6 +64,10 @@ Meanwhile:
- [Email contents and formatting](using_service_desk.md#email-contents-and-formatting)
- [Convert a regular issue to a Service Desk ticket](using_service_desk.md#convert-a-regular-issue-to-a-service-desk-ticket)
- [Privacy considerations](using_service_desk.md#privacy-considerations)
+- [External Participants](external_participants.md)
+ - [Service Desk tickets](external_participants.md#service-desk-tickets)
+ - [As an external participant](external_participants.md#as-an-external-participant)
+ - [As a GitLab user](external_participants.md#as-a-gitlab-user)
## Troubleshooting Service Desk
diff --git a/doc/user/project/service_desk/using_service_desk.md b/doc/user/project/service_desk/using_service_desk.md
index 054918343ccd95e1285bc8bd7fee59afe8005d03..5271e442707280650dedc777586e7754c1f32f0e 100644
--- a/doc/user/project/service_desk/using_service_desk.md
+++ b/doc/user/project/service_desk/using_service_desk.md
@@ -39,8 +39,8 @@ are sent as emails:
Any responses they send via email are displayed in the issue itself.
-For information about headers used for treating email, see
-[the incoming email documentation](../../../administration/incoming_email.md#accepted-headers).
+For additional information see [External participants](external_participants.md) and the
+[headers used for treating email](../../../administration/incoming_email.md#accepted-headers).
### Create a Service Desk ticket in GitLab UI