Understanding the Different Parts of an Email Address

An email address has four parts; the recipient name, the @ symbol, the domain name, and the top-level domain.

Example:

recipient.name@domain-name.domain-extension

Recipient Name

The recipient’s name is associated with a specific person or mailbox.

There are no specific rules to define who can access the email at that user name once it has been received, but it is generally assumed that the owner of that user account is the one granting access to the email it sends or receives.

The recipient’s name could be for a specific person, a department in an organization, or even for a specific automated service.

A standard length limit for a recipient name is 64 characters, and the ASCII characters A-Z, a-z, 0-9, and !#$%&’*+-/=?^_`{|}~ are allowed.

Periods are allowed in the recipient name, but there are some rules: The period can not be the first or last character, and it can not repeat consecutively, but those cases are all valid when the email address is quoted.

Valid Examples:

first.last
FirstLast2020

There are some additional rules for the recipient name, but the best practice is to limit recipient names to the ASCII characters: a-z (lowercase), 0-9, and have no more than one period which can not be at the start or the end of the recipient name.

Best Practice Example:

first.last7

The @ Symbol

This symbol separates the recipient name from the domain name.

It is a special character that is used almost exclusively for this purpose, and although it could be included as part of the recipient name, that should be avoided as it would be very confusing.

The Domain Name

Domain names are the memorable names that are typed into web browsers to go to specific websites.

It’s important to understand that the domain name could include an optional subdomain but always has a domain extension.

The domain’s extension, or top-level domain, is considered a separate part of an email address.

Valid Examples:

domain
google
subdomain.domain
www.microsoft

Top-Level Domain Extension

The top-level domain is the portion of the email address that is furthest to the right of the domain and is separated by a period.

Originally there were only seven top-level domains (.com, .net, .org, .int, .edu, .gov, and .mil), but today there are hundreds of domain extensions.

The new top-level domains sometimes indicate the country of origin, and in other cases, they are just vanity names such as .app, .cars, or .shoes.

Valid Examples:

.com
.edu
.co.uk
.xyz
.online