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Send page comments via the channels: if selected page comments (in our case comments to questions) are also send via the notification channels defined by you.
In general we do not recommend using page (question) comments.General notifications by email: those notifications are sent out by email regardless of any notification channel you define in the corresponding dialog. Please note that those notification apply to all users - no user can opt-out.
Notification templates: you can define your message templates as you like including the placeholders listed at the bottom of the tab.
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