Bonjour’s Multicast Domain Name Service (mDNS) uses the “.local” suffix to identify Bonjour-accessible devices. This is documented in the Internet Engineering Task Force (IETF) Request for Comment (RFC) 6762. It’s also recorded in the official Internet Assigned Numbers Authority (IANA) registry of Special-Use Domain Names. If your organization uses the “.local” suffix, Apple devices might not resolve your unicast DNS names or bind to your Active Directory domains.
When your organization plans its internal network, it should register a domain name for its use. If your organization uses an unregistered domain name, it should avoid all IANA Special-Use domain names. Currently, the “.home” and “.corp” DNS suffixes are not Special-Use domain names. Note that the IETF and ICANN can designate any unregistered suffix as Special Use.
You can learn more about ICANN’s name collision study and their proposal to manage collision occurrences.