Redmine

Currently issue notifications are limited to few options. If you want to exclude particular event redmine only allows settings for note, status, assignee, priority and target versions updates.
So there is no way to disable e.g. notifications for relation update.
Attached patch extends possible options for notifications. To existing ones added next events:

• Start date updated
• Due date updated
• Estimated hours updated
• Category updated
• Description updated
• Done ratio updated
• Parent issue updated
• Project updated
• Tracker updated
• Subject updated
• Attachment updated
• Relation updated
• Custom value updated