Exchange Server 2016 uses the following DNS records types:-
- SRV Record
- Host Record
- MX Record
- SPF Record
SRV resource records are DNS records that identify servers that provide specific services on the network. For example, an SRV resource record can contain information to help clients locate a domain controller in a specific domain or site.
All SRV resource records use a standard format, which consists of several fields that contain information that AD DS uses to map a service back to the computer that provides the service. The SRV resource records for domain controllers and global catalog servers are registered with different variations that enable clients to locate domain controllers and global catalog servers in several different ways.
Host records provide host name to IP address mapping. Host records are required for each domain controller and other hosts that need to be accessible to Exchange servers or client computers. Host records can use IPv4, which are A records; or IPv6 records, which are AAAA records.
A Mail Exchanger (MX) record is a resource record that allows servers to locate other servers in order to deliver Internet email by using SMTP. An MX record identifies the SMTP server that will accept inbound messages for a specific DNS domain. Each MX record contains a host name and a preference value. When you deploy multiple SMTP servers that are accessible from the Internet, you can assign equal preference values to each MX record to enable load balancing between the SMTP servers.
Sender policy framework (SPF) records to support Sender ID spam filtering. In addition, some organizations use reverse lookups as an option for spam filtering, so you should consider adding reverse lookup records for all SMTP servers that send your organization’s email.