Question : MX records - secondary mailhost - how long to switch over

Hi there,

I have an office setup with a dual broadband connection using a sonicwall TZ170 so that if one broadband connection goes down the other connection takes over.

I have also set up the MX record so that it has two entries, a primary value being the IP address of one of the static IP broadband connections and a secondary  value being the ip address of the second broadband.

What I want to know is, if I go in and perform a test where I disconnect the primary internet connection, how long it is that email gets delivered to the exchange server via the second broadband connection?

Is there a way to make it switch between the two IP addresses quite quickly but only go to a third location if those two are BOTH unavailable for a long amount of time (e.g. after 4 hours of not being able to delivery to BOTH  then try an alternative.

Thanks for any input.

Answer : MX records - secondary mailhost - how long to switch over

The emails should start to come through almost immediately. The sending server will first try the MX record with the lowest number (eg 10), and if there is no joy there, it will try the next record, and then the next (eg MX records 20, 30).

So, providing the DNS entries are being served correctly, the changeover should happen straight away.