Well I like postfix and it is fairly easy to setup, from what I have heard exim is as well. With that said you did not have a exim failure, you had a dns failu

Well I like postfix and it is fairly easy to setup, from what I have heard exim is as well. With that said you did not have a exim failure, you had a dns failure that broke the delivery of mail because exim could not map host names to ip addresses. The best way to fix that is with a monitoring setup to check that dns is working. use something like monit or nagios(much heavier) to do a local dns look up on the server box every so often, once every 5 minutes, and get an alert form a different box that does the checking. Another way is to setup a cron job that send you email and filter to a folder put a time stamp in the subject and look at it every so often to see new stuff is there, run job once an hour and filter into a folder