Board base URL is the URL which will be used as the URL base for unsubscription links in notification e-mails. It can be set in two ways:
•In Site Manager -> Settings -> Community -> Message boards -> Board base URL; from here, it can be inherited by the web parts.
•Directly in Message board web part properties.
The following rules should be followed when creating user and group message boards placed on these pages in order for the unsubscription links to work correctly:
1. When you create a user message board, which is a message board placed on a user's profile, it is recommended to set the Board base URL directly in web part properties, for example like this:
You can find a live example of this setting on the Community Site sample website.
2. When you create a group message board, which is a board placed on a group's profile, it is recommended to set the Board base URL directly in web part properties, for example like this:
3. When you create a public message board, which is a board placed on any document without a wildcard URL, the Board base URL property needn't be set.