When enabling issue tracker integration in addition to general settings, you need to specify which are to be recognized as references to issues in your tracker.
For YouTrack, you need to provide a space-separated list of Project IDs. You can also load all project ids automatically: check Use all YouTrack ids automatically and test connection to your YouTrack server. If the connection is successful, the Project IDs field will be automatically populated. Newly created projects in YouTrack will be detected by TeamCity and the project IDs list will be automatically synchronized.
For example, if a project id is TW, an issue id like TW-18802 mentioned in a VCS comment will be resolved to a link to the corresponding issue.
YouTrack provides native TeamCity integration which enhances the set of available features. For example:
To use these features, configure YouTrack.