bbPress.org

try this in your functions file

function rew_no_reply_per_forum ($reply_address) {
	$forum_id = bbp_get_forum_id() ;
	if $forum_id = 6 $reply_address =  'xxx@yyy.com' ;
	if $forum_id = 7 $reply_address =  'abd@hdhd.com' ;
	return $reply_address ;
}

add_filter ('bbp_get_do_not_reply_address', 'rew_no_reply_per_forum') ;