Document email on push service

doc/project_services/emails_on_push.md

+## Enabling emails on push
+
+To receive email notifications for every change that is pushed to the project, visit
+your project's **Settings > Services > Emails on push** and activate the service.
+
+In the _Recipients_ area, provide a list of emails separated by commas.
+
+You can configure any of the following settings depending on your preference.
+
++ **Push events** - Email will be triggered when a push event is recieved
++ **Tag push events** - Email will be triggered when a tag is created and pushed
++ **Send from committer** - Send notifications from the committer's email address if the domain is part of the domain GitLab is running on (e.g. `user@gitlab.com`).
++ **Disable code diffs** - Don't include possibly sensitive code diffs in notification body.
+
+---
+
+![Email on push service settings](img/emails_on_push_service.png)

doc/project_services/project_services.md

@@ -33,7 +33,7 @@ further configuration instructions and details. Contributions are welcome.
 | Campfire | Simple web-based real-time group chat |
 | Custom Issue Tracker | Custom issue tracker |
 | Drone CI | Continuous Integration platform built on Docker, written in Go |
-| Emails on push | Email the commits and diff of each push to a list of recipients |
+| [Emails on push](emails_on_push.md) | Email the commits and diff of each push to a list of recipients |
 | External Wiki | Replaces the link to the internal wiki with a link to an external wiki |
 | Flowdock | Flowdock is a collaboration web app for technical teams |
 | Gemnasium | Gemnasium monitors your project dependencies and alerts you about updates and security vulnerabilities |