Will this MX failover scenario work for me?
 

Hello Folks,

Just wondering if the below scenario can be possible for me?
I have say example.com domain for which mail server is configured on Private IP address 192.168.10.10 and I have two ISPs configured on firewall say ISP-A and ISP-B

IP address from ISP-A is 1.2.3.4 and ISP-B is 5.6.7.8 and both are natted to same IP address on my firewall having two MX records added on INTERNET i.e.

1.2.3.4 mail.example.com 10
5.6.7.8 mail1.example.com 20

Now if one of my ISP goes down mails coming from foreign domain will try for first entry if that is not live then it will try for second IP which should get accepted and mails should get delivered??

Am I correct?

Yes and it's something you could test yourself: just block MDA access to the first record host (for your test IP only!) and you should see emails arriving at the second host.

Ok but any ways second MDA will be down considering the link failure so I shld receive mails, right??

I don't understand what you are trying to say. I suggest you go test your scenario and post back the results.