I have a couple of DNS records with 2 or more IP addresses, for example, the A records for our email server is "mail.example.com" and have 2 IPaddress:
mail.example.com 188.8.131.52 mail.example.com 184.108.40.206
Each IP address belong to a different ISP. Sometimes, when one of those IP's are unavailable, some applications on users's computers (like Outlook) get stocked with only the first IP address on the A record they received from the DNS Server, even though it receives 2 IP's, Outlook does not try with the other IP. I've seen this with other applications as well. When I run "ipconfig /displaydns" I see that the DNS have delivered the 2 IP's for the A record, but the app is only using the first one.
We use Amazon Route 53 to manage DNS, and to workaround this I'm using "Health Checks" and then the DNS response based on the availavility of the IP's.
My question is, is it normal that applications use only the first IP address they find on the DNS record? Is there any other way to make the applications alternate between the IPs on a given DNS record or this behave depends on the app?