Use ispconfig as a backup MX?

[vwpete]

Hello,
I would like to setup a backup mx service on my ispconfig 3.2 server. I have read through my manual and have concluded that the way to do this would be the following.
configure email routing
Domain = exampledomain.com
type= smtp
No MX lookup = unchecked
Destination = mail.exampledomain.com
sort by = 5
active = checked

configure Relay recipients
Relay recipient = @exampledomain.com
active = checked

This assumes also that my dns mx Auxiliary Info records are set correctly so that this ispconfig server has a higher AI than the primary mail server at “mail. exampledomain.com”
so is this the right way to go about it?

Cheers