| `List-Id`| The path of the project in an RFC 2919 mailing list identifier. You can use it for email organization with filters. |
| `X-GitLab-(Resource)-ID` | The ID of the resource the notification is for. The resource, for example, can be `Issue`, `MergeRequest`, `Commit`, or another such resource. |
| `X-GitLab-Discussion-ID`| The ID of the thread the comment belongs to, in notification emails for comments. |
| `X-GitLab-Group-Id`**(PREMIUM)** | The group's ID. Only present on notification emails for epics. |
| `X-GitLab-Group-Path`**(PREMIUM)** | The group's path. Only present on notification emails for epics. |
| [`X-GitLab-NotificationReason`](#x-gitlab-notificationreason) | The reason for the notification. This can be `mentioned`, `assigned`, or `own_activity`. |
| `X-GitLab-Pipeline-Id`| The ID of the pipeline the notification is for, in notification emails for pipelines. |
| `X-GitLab-Project-Id`| The project's ID. |
| `X-GitLab-Project-Path`| The project's path. |
| `X-GitLab-Project`| The name of the project the notification belongs to. |
| `X-GitLab-Reply-Key`| A unique token to support reply by email. |
| `List-Id` | The path of the project in an RFC 2919 mailing list identifier. You can use it for email organization with filters. |
| `X-GitLab-(Resource)-ID`| The ID of the resource the notification is for. The resource, for example, can be `Issue`, `MergeRequest`, `Commit`, or another such resource. |
| `X-GitLab-Discussion-ID` | The ID of the thread the comment belongs to, in notification emails for comments. |
| `X-GitLab-Group-Id` | The group's ID. Only present on notification emails for [epics](../group/epics/index.md). |
| `X-GitLab-Group-Path` | The group's path. Only present on notification emails for [epics](../group/epics/index.md) |
| [`X-GitLab-NotificationReason`](#x-gitlab-notificationreason) | The reason for the notification. This can be `mentioned`, `assigned`, or `own_activity`. |
| `X-GitLab-Pipeline-Id` | The ID of the pipeline the notification is for, in notification emails for pipelines. |
| `X-GitLab-Project-Id` | The project's ID. |
| `X-GitLab-Project-Path` | The project's path. |
| `X-GitLab-Project` | The name of the project the notification belongs to. |
| `X-GitLab-Reply-Key` | A unique token to support reply by email. |