I have 2 VPS with knownhost. I have a client that email is very important with them. Can I setup dual delivery email for them? It means that email delivery to 2 VPSs for one domain. How to configuration dual delivery email ?
Same domain name on 2 different VPSs? Not sure you can do that but if one's like .com and the other is .org you could. One will have to be the primary (.com) and create all the same addresses on the secondary (.org). And then for every email address you create (on the .com) make a forwarder to forward it to the other (.org). You may also be able to use the domain forwarder function although I am not sure that this will leave a copy on the primary server. I say give it a try and see what happens, you can always delete it if it doesn't work.
Might be something you can do with MX records or through a third party too, but not that I am aware of myself.