The Maximum and Minimum for Email Address Length

Wondering what the longest-possible email address is? How about the shortest, and how long can the username alone be? Find here the maximum and minimum length for an email address.

First, Mounting Pressure

Precious and (increasingly) scarce helium always tries to escape. It is light enough to gather in the upper atmosphere and overcome earth’s gravity entirely with relative ease to veer off into space.

Trapped inside a balloon it will, of course, take the balloon with it. As the pair rises over men, hills, houses, and mountains, the pressure inside relative to the thinner and thinner atmosphere outside also rises and mounts.

Around 33 000 feet (10 000 m), it turns out, is the highest a typical party balloon will rise.

With that out of the way, let’s see to which heights (and lengths) we can take an email address:

The Maximum and Minimum Length for an Email Address

Every email address using standard SMTP email is made up of three parts:

• the username part (what precedes the ‘@’ sign),
• the @ sign itself, and
• the domain part (what comes after the ‘@’ sign),

each with their own maximum and minimum length.

Email Username Maximum Length

The username for an email can be up to 64 characters long, and it must be at least one character long.

A character, in the case of SMTP email, is an 8-bit value. Some email standards allow for special characters in email addresses. If a special character takes up more than 8 bits, it will also occupy multiple “characters” in the SMTP standard. The maximum length of the username part consequently shrinks (as counted in visible characters).

Examples

sixtyfouristhenumberofcharsyoucancountinthisemailaddressusername

This username part has exactly 64 characters (all of them allowed in an email address). No email username should safely be longer than that.

i

This is a particularly short email username.

Email Domain Maximum Length

The maximum length for email domain names is not specific to email. The general limits for domains apply.

The whole domain part can be up to 253 characters long for DNS.

This includes two dots to separate the domain name’s three parts, so at most 251 characters remain. The parts of a domain name are (read from the end):

• the top-level domain (e.g., “com” or “org”, always required),
• the domain name (what comes immediately before the top-level domain and separated from it with a dot; e.g., “ladedu”) and
• the sub-domain (in front of the domain and again separated with a dot; entirely optional).

Top-level Domain

The shortest top-level domains are two characters long, such as “li,” “ai” or “pn.” The top-level domain can be up to 63 characters long.

Longer top-level domains do not increase the maximum length for an email address. The longer top-level domain is deducted from the maximum length of the sum of the domain part’s other components.

Though discouraged, a top-level domain alone can receive email.

Domain and Sub-domain

The domain can be up to 63 characters long and as short as 1 character. Sub-domains can be of any length (provided the full domain name does not exceed 253 characters).

Minimum and Maximum Email Address Domain Name Examples

this-is-a-very-long-domain-name-that-is-exactly-two-hundred-n.fifty-three-characters-long-including-the-dot-and-the-subdomain.and-the-tld-which-is-ladedu-com-so-if-you-count-all-the-letters.and-the-dots-you-will-get-two-hundred-n-fifty-three.ladedu.com

This domain is 252 characters long, the maximum length for a domain that accepts email.

li

This is a particularly short domain.

Email Address as a Whole

The parts can sum up to a maximum of 318 characters (64 for the email username, one for the @, and 253 for the domain name, but that is not the maximum length for an email address.

SMTP email does not allow addresses longer than 254 characters itself:

• The sender and recipient’s addresses must not exceed 256 characters,
• including “<” and “>” to delimit them.

Maximum and Minimum Length for an Email Address: Overview

Email Address Part	Max and Min Lengths in Characters
Username	1–64
@	1
Sub-domain and domain	1–63
Top-level domain	2–63
Whole email address	4–254

Speaking of email addresses and space: Can an Email Address Have a Space?

Maximum and Minimum Length for an Email Address: Examples

i@li

At its minimum of four characters, this is the shortest an email address can currently be.

sixtyfouristhenumberofcharsyoucancountinthisemailaddressusername@this-loong-domain-name-is-exactly-one-hundred-and.eighty-nine-characters-long-including-the-dots-so-if.you-count-all-the-letters-and-dots.you-will-get-one-hundred-and-eighty-nine.ladedu.com

With 254 characters, this is an example of the maximum email address length.

(The maximum and minimum length for an email address updated April 2024)