The IMAPITable::CollapseRow method collapses a table category and removes it from the table view. The rows are collapsed starting at the row identified by the PR_INSTANCE_KEY property pointed to by the pbInstanceKey parameter. The number of rows that are removed from the view is returned in the contents of the lpulRowCount parameter.
Notifications are never generated for table rows that are removed from a view as the result of a collapse operation.
When a row that is defined by a bookmark is collapsed out of view, the bookmark is moved to point to the next visible row.