As this first iteration of the inbox will only have mentions there is only one type of card Mention card with a read and unread state.

The inbox will be part of the elements of the navigation bar and it will show the amount of unread notifications that are pending for the user. When noting has been selected it will have an "empty" state.

As the user can have more then one account and as of this moment the navigation side panel does not differentiate between content form different accounts, then the inbox will be showing mentions form all accounts that the user has. For this their is a filter button so that the user can filter out their notifications depending on the account that they want to see notifications for.

When a notification is selected it will show the content of the content that has been made, in this case is a comment in document so we have to open the discussion tab.

The inbox will also have options to mark the notifications as read as well as delete the items.