localpartdomaintld

Localpartdomaintld is a descriptive shorthand used to refer to the three components that comprise a typical email address: the local part, the domain name, and the top-level domain (TLD). It is not a formal standard, but a convenient label found in documentation, teaching materials, and parsing schemas to emphasize how an address can be decomposed for processing.

The local part is the portion before the at-sign and designates a mailbox or user within a host. It can include letters, digits, and a set of allowed special characters, and may be structured as dot-separated segments or as quoted strings in some contexts. The domain part follows the at-sign and identifies the destination domain; it is a domain name that can be resolved through DNS, and in some cases may be written as an IP literal in brackets. The top-level domain is the rightmost label of the domain, such as com, org, or net, and includes newer gTLDs; TLDs are managed in the DNS root by global naming authorities.

In practice, software often parses an address into local and domain components, validates syntax, and then resolves mail delivery routes via MX records. Internationalization considerations allow non-ASCII characters in certain components, using mechanisms such as IDN encodings, while compatibility layers may impose stricter ASCII rules. The term serves as a mnemonic for understanding routing, storage, and privacy implications, rather than representing a separate standard.