What is a dotted hostname in the context of email and DNS records?

In the context of email and DNS records, a 'dotted hostname' can be understood as a specific name given to a computer within a network to identify it. It's often the leftmost part of a Fully Qualified Domain Name (FQDN), and can be a subdomain (e.g., mail.example.com). While some argue that there's no significant difference between a hostname and a domain name at the DNS level, for email purposes, a valid hostname should resolve to a valid IP address to pass authentication checks. RFC 952 specifies that hostnames consist of alphanumeric characters (starting with a letter) and hyphens. Best practices suggest using a fully qualified domain name (FQDN) as the hostname that resolves to the server's IP address. Even with a hostname, it's important to set up DNS records like MX and SPF for email delivery and security. If dealing with complex hostname issues, engaging an expert is recommended. Finally, it is recommended you don't use the raw hostname for 'From' addresses but rather a subdomain.

In the context of email and DNS records, a hostname is a name assigned to a computer for identification on a network, often the leftmost part of a Fully Qualified Domain Name (FQDN). While sometimes used interchangeably with 'domain name', a hostname refers to a specific machine, while a domain name indicates a network location. Hostnames can be subdomains, and should ideally be FQDNs resolving to a valid IP address for email deliverability. Despite not being recommended for general email 'From' addresses, hostnames can still have MX and SPF records. In email addresses, the hostname is the part after the @ symbol, indicating the mail server responsible for handling the email.

Experts have varying perspectives on 'dotted hostnames'. One opinion suggests that there is no real distinction between hostnames and domain names within the DNS infrastructure, and SMTP operates at a higher level. Other opinions suggest it must exist and resolve to a valid IP address to pass email authentication checks. The DNS system is structured hierarchically, and for complex issues, the best course of action is to engage an expert.

Documentation defines a hostname as a domain name assigned to a host computer, resolving to one or more IP addresses. It acts as a label identifying a device on a network. The syntax mandates alphanumeric characters, starting with a letter, and optional hyphens. A Fully Qualified Domain Name (FQDN) incorporates the hostname and all parent domains, up to the root, offering an absolute location within the DNS hierarchy. Hostnames are used in DNS records to map domain names or subdomains to IP addresses, enabling access using human-readable names.