backup mail server

[TAG]

Hi,

I have two mail servers - on is located in a different country - My
question is how do I become a backup for that other server in the event
that it goes down or looses connectivity??

I have added entries into DNS so as the two severs are secondary MX's
for each other..  BUT what needs to be done on the qmail side so that it
will accept these messages and queue them until they can be dilivered??

Thanks
Tonino