Currently this application only allow 1 server to be designated NAB server. This means that any Notes Internet Password reset will be done on that NAB server.
For company with more than 1 mail server I think that it make more sense for Notes Internet password reset be done on respective user's home/mail server. This way, there will be no need to wait for NAB replication to occur.
Not sure how much difficulties this is but I know that it is possible because I saw a manually develop redirect script on Domino nsf that does lookup to user's home mail server and redirect the login there.