The existing Exchange 2010 server located at office with public IP, but not configure as primary MX. It pull email from external mail server which works as the primary MX.
We want to setup secondary email server that works as secondary MX, when the pri mx server down, the sec mx server take over automatically. The existing exchange server will remain located at office to serve as active directory, the pri mx can be located else where and it can be Linux. The exchange server can configure as sec mx.
If you have better suggestion then what was mentioned above, please feel free to comment.
11 freelancers are bidding on average $95 for this job
Exchange server licensing is pretty costly. You may opt for free linux mail server for backup. If fund is not an issue you can go with it. We can have a discussiion on this if you want
This is easily accomplished in DNS and on your local firewall. That being said, you might consider Postini or a similar cloud based spam filter, which would accomplish this and be more reliable.