Dear All, I have been using centos 5.1 for quite some time as out DNS and mail server and been workin fine i use sendmail as my mail server i did setup a backup mail server as per docs and ran th dns test from http://www.checkdns.net and it says both the mail servers are fine but i would like to know the following how would i really know if my main primary server is down all my mails r goin to my secondary mail server and when my primary is up are the mails copied back to my primary i did put down my mail server for abt 3 hrs cause cant keep it down for long but did not really see anything also are there any websites that can chec both my mail servers correctly apprecite and thnaks -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.