I am running everything in Azure - 2013 Exchange which is Hybrid and 2010 Sp3 Exchange.
Since IPs might change when machine is shut I was reading somewhere that it is advisable to use CNAME instead of A records so instead of pointing to IP, I could use CNAME and point to Exchange2013 hostname
So, I need two records mail and autodiscover for 2013 server. Also, my internal Domain is contoso.local (non routable) and I setup DNS forward lookup zone for domain that is routable - externaldomain.com
So, I have local domain - contoso.local and external domain setup as forward lookup zone in internal DNS- externaldomain.com
what internal DNS records to I need to setup? Can I setup cname records in both forward lookup zones?
Contoso.local DNS forward lookup zone
CNAME autodiscover.contoso.local points to exchange2013.contoso.local
MX record mail.contoso.local points to exchange2013.contoso.loca
Externaldomain forward lookup zone on internal DNS
CNAME mail.externaldomain.com points to exchange2013.contoso.local
CNAME autodiscover.externaldomain.com points to exchange2013.contoso.local
Please note that because I used digi cert and it doesn't support non-routable domains such as contoso.local, they advise to use external names for exchange server