What is the maximum length of a valid email address? Is it defined by any standard?

 

The maximum length of a valid email address is not explicitly defined by the Internet email standards (RFC 5322 and RFC 5321). These standards specify the structure and format of email addresses but do not set a maximum length for the entire address. Instead, they provide guidelines for the length of individual components within the address.

In practice, the maximum length of an email address is determined by the email service providers, email clients, and server software. Most modern email systems allow relatively long email addresses, but there is no universal maximum length.

For example, Gmail, one of the popular email service providers, allows email addresses up to 254 characters in length before the "@" symbol. However, the overall length of an email address, including the local part (before "@") and the domain part (after "@"), should not exceed 320 characters.

Here's an example of a long email address that is valid according to the guidelines:

css

this_is_a_long_local_part@subdomain.example.com

In this example:

• The local part is "this_is_a_long_local_part," which is 28 characters long.

• The domain part is "subdomain.example.com," which is 19 characters long.

• The overall email address is 48 characters long.

It's worth noting that while long email addresses are technically allowed, using very long email addresses may not be practical in all situations, as they could lead to usability and display issues in some email clients and web forms. Therefore, it's a good practice to keep email addresses reasonably short and user-friendly.