An email address is a unique identifier that lets you send and receive digital messages. It’s basically your mailing address for the internet. All email addresses follow the same basic structure: username@domain.
We use our email every day without giving it much thought — signing up for accounts, logging in, verifying our identities, and recovering passwords. In many ways, the email address has evolved into the thread that ties much of our online identity together.
How much do you actually know about your email address? Let’s explore what it’s made of, some common uses, and advice on keeping yours private.
- The evolution of the email address
- Elements of an email address
- Valid and invalid email addresses
- How people use email addresses
- Why protecting your email address is important
- Keep your email address private
The evolution of the email address
When email was invented in 1971, it served a purely functional purpose. It was a way for people on the same network to communicate digitally via simple messages on the ARPANET, the precursor to the internet. As the internet grew, email addresses became central to our digital lives.
Today, your email address is essential for nearly everything. It’s how you communicate, log in, and access sensitive information, such as your tax details. What started out as an online mailing system now holds the keys to your entire life online.
The elements of an email address
Email addresses are made up of three parts: the username (also known as “local-part”), the @ symbol, and the email domain name.
The username
Your email username is the part of an email address that identifies you within the email service.
When creating your username, you can use your real name or a pseudonym. Each has its own benefits; for example, using your real name works well in professional contexts as it is recognizable. Pseudonyms offer greater privacy but look less credible in formal communications, such as when applying for a job.
Most email services force you to choose between privacy and professionalism, but email aliases allow you to have the best of both worlds. Instead of giving out your real email address everywhere and risking unwanted messages, you can create unique aliases for different websites and services. All messages still arrive in the same inbox, but the alias keeps your primary email address private. If an alias starts receiving spam, you can simply disable it. Find out how email aliases work.
The @ separator
The @ symbol separates your username from the domain name and tells the email system where to route your message. Without it, the system wouldn’t know which server to deliver to, and you would have a delivery failure instead.
When designing the first network email system in 1971, Ray Tomlinson looked for a character on the keyboard that could separate the user from the host computer. He chose the @ symbol, which already meant “at,” making addresses like user@host read naturally as “user at host.”
The domain name
What is an email domain? It’s the part of an email address that signals which email provider handles your messages. It comes after the @ symbol, such as “proton.me” or “gmail.com.” An email domain typically has two parts:
Second-level domain (SLD): The name of the email service (e.g., “proton”)
Top-level domain (TLD): The suffix at the end (e.g., “.com”)
Some domains can also include additional parts, such as subdomains. For example, addresses like “user@mail.example.com” or “user@department.university.ac.uk” contain extra levels that help route emails within larger organizations or networks.
You’ve likely come across different TLDs and wondered what they all mean. TLDs indicate the domain’s origin, and some common ones include:
.com: For commercial use, and the most widely recognized TLD
.org: For organizations such as nonprofits
.net: Originally for networks, but now used generally
.edu: For educational institutions
.gov: For government agencies
When creating an email address, most of us use the domain provided by the email service by default. Businesses and professionals, however, often use a custom email domain to match their brand; for example, instead of “help.yourbusiness@proton.com,” the address would be “help@yourbusiness.com.” If you’re running a business or a personal brand, setting up a custom email domain helps to signal credibility to clients and partners.
Valid and invalid email addresses
Email addresses follow a set of rules, and if an address breaks them, you won’t be able to create an account or deliver an email. Here are the basic rules:
Email usernames:
- Can include upper and lower case letters
- Can include numbers
- Can include certain special characters, such as periods, hyphens, underscores, dollar signs, exclamation marks, and others
- Cannot start or end with a period
- Cannot have two consecutive periods
- Cannot contain spaces
Email domains:
- Must include both SLD and TLD
- Can include letters, numbers, and hyphens
- Cannot start or end with a hyphen
| Examples of valid email addresses | Examples of invalid email addresses |
|---|---|
| eric.norbert@proton.me | eric..norbert@proton.me |
| er1c_n0rbert@proton.me | .ericn0rbert@proton.me |
| ericnorbert+newsletter@proton.me | ericnorbert.proton.me |
| eric~n0rbert@proton.me | eric norbert@proton.me |
| hello@ericnorbert.com | ericnorbert@proton |
| contact@ericnorbert.co.uk | ericnorbert@-proton.me |
How people use email addresses
Today, an email address wears many hats, and we use it across our digital and offline lives.
Personal use
Even with the popularity of social media and instant messaging apps, email remains one of the easiest ways to stay in touch with friends and family. It also serves as a searchable record of your transactions, as it is where your online receipts, travel and appointment confirmations, and subscription renewals land.
Professional use
In work environments, email is the backbone of communication. It is how many teams coordinate projects, reach clients, close deals, and receive job applications. Email also creates a record of decisions, agreements, and conversations that can be referenced later — which can be especially important for sensitive information.
Official use
Many organizations are increasingly turning to email as an environmentally friendly alternative to traditional mail. In many developed economies, governments, banks, and public institutions now deliver official communications digitally as part of broader efforts to modernize services. As a result, sensitive information such as bank statements, tax forms, and government notices are often sent straight to your inbox. This makes securing your inbox even more important.
Why protecting your email address is important
With so much riding on your email address, keeping it private has never been more important. Today, companies try to get your email address at almost every turn, such as when ordering food in a restaurant. Sometimes, you’re offered a promo code for your email — that’s the equivalent of selling your digital identifier for chump change.
Once your email address is shared, you lose control over who knows it and how that knowledge is used. It could be sold to data brokers or exposed in a breach. These risks are easy to overlook, but their consequences can range from merely annoying to severe:
Spam: These are unwanted emails clogging your inbox. Our 2025 Spam Watch report shows that most marketing emails contain invisible pixel trackers and spike heavily during holidays, driving inbox overload.
Tracking: Companies can link your email to your online activity to build a detailed behavioral profile. For example, Google can connect your activity across services, like searches on Google Search, videos watched on YouTube, and places visited using Google Maps — all because you were simply signed in to your Gmail account.
Phishing: Scammers may send you fraudulent emails designed to trick you into revealing personal information, which can lead to identity theft, financial loss, or unauthorized access to your accounts.
Data breaches: If companies storing your email, passwords, or payment details are hacked or leak data, your personal information can be exposed to cybercriminals, leading to account takeovers, identity theft, or financial fraud.
Keep your email address private
The simplest way to protect your email address is to share it only when necessary, such as when setting it as a recovery email for an account.
Whenever you’re asked to give out your email address — whether to sign up for a newsletter, create an account, download content, or unlock a discount — remember that you don’t always have to. If there’s an option to continue without sharing it, such as checking out as a guest, choose that instead.
If that’s not possible, create email aliases for different purposes and manage them with Proton Pass. Each alias forwards emails to your Proton Mail inbox, and you can reply from it just like your regular address. Using a unique alias for each service also makes it easy to spot when a company shares your information — for example, if an alias used for one website starts receiving ads from another.
Proton Mail acts as the secure inbox behind your aliases. It provides built-in protections for blocking email trackers and phishing, managing subscriptions easily, and advanced spam filters to help you stay in control. It also includes Dark web monitoring to alert you if your data appears in breaches, and Proton Sentinel for advanced account protection against targeted attacks.
Because all Proton apps share the same account, you can use Proton Mail’s inbox protections, Proton Pass aliases, and other Proton privacy tools together, even on a free plan.
Proton Mail offers a European alternative to Big Tech email services like Gmail and Outlook: we never show ads, track your activity, use your emails to train AI models, or share your data with anyone. We use end-to-end and zero-access encryption to keep your data safe, meaning not even Proton can access the contents of your inbox. And because Proton Mail is open source, anyone can verify how it works, so you don’t have to simply trust us with your data.
