We recently setup a multi wan router to leverage two separate ISP’s – one is our original T3 and the other is business cable model. All traffic other than SMTP traffic goes out whichever link is less used, and SMTP traffic is pinned to the original T3 link. Our current MX record points to our hardware spam filter which has a public IP address from the T3 ISP. The question I have is what is the best way to create a secondary MX record in the event my T3 ISP goes down. Currently if that happens I will still have internet traffic but not email. I know i can create a second MX record with a lower cost (say 20), but wasn’t sure exactly the correct method for having it kick in, still send to my spam filter to be forwarded to my exchange server. Any information would be greatly appreciated, thanks!