I run a in-house Exchange server for all my email needs. Every once and a while the server that is running all the VMs (Virtual Machines) freezes up. It requires me to restart the server and after that it works fine for the longest time. But when it does go down some of my email gets bounced. This is because I only have one exchange server.
I have a couple of VPS’ over at RamNode. One of them being a 128MB SSD-cached VPS. I was going to make this into a nameserver but a backup MX is what I need more. I was researching on how to do this with sendmail. I could not get this to work. I found a article on how to do the same thing with Postfix. I went through the steps and setup the server. I then disabled the network card on my Exchange server and using GMail sent an E-mail to my e-mail address. I waited a few seconds and updated the mail queue, the page updated saying I had one e-mail in the queue. I opened the email and it was the test mail that I had sent a few seconds ago. It said the statues was it was trying to relay it to my exchange server but it was not responding. I enabled the networking on the exchange and told postfix to process the queue (This is not necessary it tries to send it every 30 minutes or so, I was just lazy and did not feel like waiting.). After I did that outlook said I had a new email and there it was. The e-mail I had sent while the exchange was down. I looked at the mail headers and it says the e-mail was received by MX2 which is the mail server I just setup.
Here is the instructions I used to set this all up. Now instead of paying a company $10 a month. I just spend $14 a year on a small VPS and do it my-self.