Email addressing uses domains. A domain is a directory structure for network address naming. A domain can have one or more subdomains. The domain and subdomains of an address can be compared to the hierarchy of a file system. Just as a subdirectory is considered to be inside the directory above it, each subdomain in a mail address is considered to be inside the location to its right.
The following table shows some top-level domains.
Table 14–7 Top-Level Domains
Domain |
Description |
---|---|
com |
Commercial sites |
edu |
Educational sites |
gov |
United States government installations |
mil |
United States military installations |
net |
Networking organizations |
org |
Other nonprofit organizations |
Domains are case insensitive. You can use uppercase, lowercase, or mixed-case letters in the domain part of an address without making any errors.