Anatomy of an Email Address

What’s allowed in an e-mail address? Let’s break down the syntax.

If you have an email address, likely you barely notice how an address works. For example, can you use odd characters like a period or underscore or asterisk in an email address?

Email addresses have two parts separated by the @ (called ‘at’) symbol, a local-part and a domain, as in . jane.doe is the local part and is the domain. Mail servers are software that use the domain to find the server that handles your email. Once your email arrives at your email server, the local part is used to deliver email to your mailbox.

More interesting, are the rules around email addresses. The local part can be up to 64 characters while the domain part can be up to 255 characters. And there’s only one @ symbol allowed, between the local and domain parts.

The local part can be uppercase and lowercase Latin letters, A to Z and a to z, as well as digits 0 to 9, special characters !#$%&’*+-/=?^_`{|}~, and a dot or period in some cases. jane.. is not allowed but ‘jane..doe’ works.

The domain part has stricter rules. Only letters, digits, and hyphens are allowed.

What actually works, however, depends on your mail server. Probably it’s a good idea not to get too crazy or fancy the next time you create an email address!

Learn More

Email Address


  • Tim Slavin

    Tim is an award-winning writer and technologist who enjoys teaching tech to non-technical people. He has many years experience with web sites and applications in business, technical, and creative roles. He and his wife have two kids, now teenagers, who are mad about video games.

Also In The December 2018 Issue

Create colourful geometric patterns in SketchUp inspired by the Great Mosque of Cordoba.

Learn how to use animated GIFs to create proper animation loops in Scratch.

Create an electronic obstacle course and test the steadiness of your hands as you navigate through.

What’s allowed in an e-mail address? Let’s break down the syntax.

Throwing your old tech in the trash is bad for the environment. Check out some safer, cleaner alternatives.

New, crafty mods that’ll push your Minecraft design skills to new levels.

Part philosophical paradox, part coding puzzle, quines are sure to tease and challenge your brain!

5 questions with the designer pushing innovation in 3D printed clothes.

All work and no play makes it harder for kids to learn, especially those with anxiety and learning disabilities.

Dive into the nuts & bolts of storing pictures and files on your computer.

A clever AI is creating twisted, surreal art. Math or magic?

Two doors hide a zonk, and one door hides a prize. Can probability & statistics help you pick the right one?

How can you tell if a credit card number is valid or invalid? Meet the Luhn algorithm, one of many checksums helping us keep the internet in order.

Learn about the Destination Dispatch algorithm and create your own robotic lift.

Grab your friends & disconnect from the digital world with these fun science & tech board games.

Interesting stories about computer science, software programming, and technology for December 2018.

Links from the bottom of all the December 2018 articles, collected in one place for you to print, share, or bookmark.

Interested but not ready to subscribe? Sign-up for our free monthly email newsletter with curated site content and a new issue email announcement that we send every two months.

No, thanks!