
The message subject contains the ID of an issue in the same project. YouTrack uses these values to thread comments when a recipient replies to notifications that are sent when an issue is created or updated in the project.

This is a standard method of parsing MIME-encoded messages. The values for the message-id/ in-reply-to properties in the message header match a previously processed email message.

YouTrack matches an incoming message to an existing issue under the following conditions: When YouTrack detects that an incoming message is related to an existing issue, the body of the message is added to the issue as a comment. Like any issue that is created manually, YouTrack assigns the issue an ID in the selected project. The reporter can either be the message author or a default user. The mailbox rule that processes the email message determines which user is set as the reporter. The message body is copied to the issue description. The message subject is copied to the issue summary. YouTrack uses the following information from an email message to create a new issue: If YouTrack cannot find any values that associate an incoming message with an existing issue, a new issue is created. The messages are processed according to the mailbox rules that are defined for the project. Each message is parsed and analyzed by YouTrack. This integration pulls email messages from an external mail service.

The Mailbox Integration transforms incoming email messages into issues and comments in YouTrack.
