Q: Does Azure DNS support reverse lookups?
A: In July 2014 Microsoft added support for pointer records that enables reverse DNS for the cloud service VIP (the Internet-addressable IP address of the cloud service). This is documented in the Microsoft blog post "Announcing: Reverse DNS for Azure Cloud Services." To use the reverse DNS lookup, you have to opt-in to the service and specify the DNS suffix that will be used for the reverse lookup:
Set-AzureService –ServiceName "savilltech101" –Description "savilltech101 with Reverse DNS" –ReverseDnsFqdn "savilltech101.cloudapp.net."
You can also add the reverse lookup when creating a cloud service by adding -ReverseDnsFqdn as part of the New-AzureService cmdlet.
The reverse FQDN can also point to a vanity domain (your domain—e.g., websrv.savilltech.net), provided that websrv.savilltech.net is an alias (CNAME) on your DNS server (in this case savilltech.net) that resolves to the cloud service DNS name (e.g., savilltech101.cloudapp.net). Basically this check is done by Azure to ensure you actually own the DNS name for which you're trying to configure reverse DNS.
If someone performs a reverse IP lookup for the IP address of your cloud service VIP, it will resolve to the configured FQDN.
This functionality doesn't apply to the dynamic IP (DIP) addresses that are assigned to virtual machines within a cloud service. If you need reverse DNS for DIPs, you need to use your own DNS service.