bp_activity_at_name_send_emails( BP_Activity_Activity $activity )

function bp_activity_at_name_send_emails( $activity ) {
	// Are mentions disabled?
	if ( ! bp_activity_do_mentions() ) {
		return;
	}

	// If our temporary variable doesn't exist, stop now.
	if ( empty( buddypress()->activity->mentioned_users ) )
		return;

	// Grab our temporary variable from bp_activity_at_name_filter_updates().
	$usernames = buddypress()->activity->mentioned_users;

	// Get rid of temporary variable.
	unset( buddypress()->activity->mentioned_users );

	// Send @mentions and setup BP notifications.
	foreach( (array) $usernames as $user_id => $username ) {

		/**
		 * Filters BuddyPress' ability to send email notifications for @mentions.
		 *
		 * @since BuddyPress 1.6.0
		 * @since BuddyPress 2.5.0 Introduced `$user_id` and `$activity` parameters.
		 *
		 * @param bool                 $value     Whether or not BuddyPress should send a notification to the mentioned users.
		 * @param array                $usernames Array of users potentially notified.
		 * @param int                  $user_id   ID of the current user being notified.
		 * @param BP_Activity_Activity $activity  Activity object.
		 */
		if ( apply_filters( 'bp_activity_at_name_do_notifications', true, $usernames, $user_id, $activity ) ) {
			bp_activity_at_message_notification( $activity->id, $user_id );
		}

		// Updates mention count for the user.
		bp_activity_update_mention_count_for_user( $user_id, $activity->id );
	}
}