I run AliasFleet, an email alias service: it gives every website its own email address, which forwards to your real inbox, so a leaked address can be switched off without touching anything else in your life. Before any of that makes sense, this page answers the basic question properly. An email alias is an extra address that is not your inbox: mail sent to it forwards to your real inbox, and the sender never learns the real address. That is the whole idea, and everything else is detail.
How an email alias actually works
An alias is a mail-routing rule, not a mailbox. When someone sends a message to your alias, the receiving server looks up the rule, swaps the alias for your real address, and delivers the message as normal. The message itself is not changed. This is defined in the SMTP specification itself: RFC 5321, section 3.9.1 says the server "replaces the pseudo-mailbox address in the envelope with each of the expanded addresses in turn; the rest of the envelope and the message body are left unchanged."
A concrete example. You create shop@yourhandle.aliasfleet.me for an online store and hand that address to the store. Their order confirmations travel to the alias, the alias forwards them to your real inbox, and the store never sees the address underneath. One alias, one site. Your alias list becomes a map of exactly who holds which address, which is the part that pays off later.
From the sender's side nothing looks unusual. The alias sits in the To field like any address, and replies to it route back through the same rule. What the alias never has is storage. There is no mailbox to fill up, no quota, no login page. Creating an alias is creating a rule, deleting it is removing the rule, and pausing one keeps the rule but stops the flow. A noisy sender goes quiet without you losing the address history.
The four kinds of alias
Most writing about aliases mixes up four different things. They all forward mail, but they are not the same tool.
Plus addressing. If your address is name@gmail.com, then name+shopping@gmail.com is yours too, and the mail lands in the same inbox. Gmail, Outlook.com, iCloud, Proton and Fastmail all accept the plus form, so it costs nothing and needs no setup. Its honest verdict: a filing system, not privacy. The real address sits inside the alias for anyone to strip out. There is no off switch, and some signup forms reject the + character outright.
Provider aliases. Your provider gives you extra addresses inside its own walls. Outlook.com lets you add a new address to your Microsoft account; iCloud Mail lets you add a few aliases to your iCloud address. These are real addresses and they cost nothing. The trade is reach: the alias belongs to that one account and follows that provider's rules. Leave the provider and the aliases go with you.
Relay or masked addresses. Services like Firefox Relay and DuckDuckGo Email Protection generate a random forwarding address for each site and pass the mail through to your inbox. The idea is the same as a dedicated alias, with the provider's own interface and limits wrapped around it. Handy if you live in that provider's ecosystem, awkward outside it, and the random addresses are hard to manage by memory.
Dedicated alias services. This is the full version: an account whose job is aliases, with per-site addresses, individual pause switches, and reply routing so your answers come from the alias. It is what we built AliasFleet for. The free tier covers 10 active aliases with a verified destination, and the creating aliases guide in our docs walks through the product itself. The honest trade is the price once you outgrow the free tier, and the trust you place in the provider's forwarding servers. For the step-by-step comparison of all the methods, see how to set up an email alias.
What an alias is not
Five things get confused with aliases constantly. Clearing them up is worth the space.
Is an email alias a second email account?
No. A second account has its own login, its own storage, and mail that sits in it. An alias has none of those. Everything addressed to an alias arrives in your one real inbox. If you have to check two places, you have two accounts, not an alias.
Is it the same as a distribution list?
No. A distribution list is a one-to-many broadcast: one message goes to the list and every member gets their own copy in their own inbox. An alias is one-to-one: one address routes to one inbox. They serve opposite directions.
What about a shared mailbox?
Also no. A shared mailbox is one inbox that several people open together, like a support queue. An alias is one address that one person receives from. Shared mailboxes are about teams. Aliases are about separating your own identities.
What is a catch-all, then?
A catch-all is a domain-wide net: any address at the domain that does not exist still lands somewhere. An alias is the opposite, a single named address you created on purpose. Catch-alls collect the unknown. Aliases route the known.
Is an alias the same as a temp-mail address?
No, and this one matters to us. A temp-mail address is a stranger's inbox you borrow for ten minutes. It expires, you do not control it, and you cannot rely on it for anything that matters, while an alias is your own address on your own account. It persists, you manage it, and you can receive password resets and order history on it for years.
What email aliases are for
With the definitions out of the way, the uses reduce to a short list. Aliases keep spam quarantined, because a noisy alias gets paused instead of polluting your inbox. They contain breaches, because a leaked per-site alias tells you exactly who leaked it and dies alone. They organise your life, because the alias list is a readable map of your accounts. And they give small businesses professional addresses like info@ and support@ without running extra inboxes.
One honest gap I should state plainly: I have never found a trustworthy public number for how many people use aliases, so I will not quote one. The search data says the question is being asked more every month. That is all I can verify, and it is enough.
Where the protection stops
An alias changes the address a sender holds. It does not change anything else about email.
It does not encrypt your mail. An aliased message travels the same servers, in the same readable form, as any other message, and if you need the content itself to be private from the servers in between, that is a different technology and a different article.
It does not hide the path. Mail headers still record the servers that handled the message, and a determined recipient can see the machinery. An alias keeps your address out of a sender's database. It is not a disguise.
It cannot protect an address you already handed out. The real address you have used for a decade sits in hundreds of databases, and no alias setup fixes that. It only stops the list growing, which is still the most valuable part.
And it does not survive your own reply. If a site emails your alias and you answer from your normal inbox, your reply carries your real address, and you have undone the alias yourself. The reply has to come from the alias too, which is why two-way reply routing is part of the product, not a bonus.
If you want the full walkthrough of getting this set up today, the set-up guide takes about two minutes per method. Start with one alias, on one site you do not care much about, and see how it feels. Most people never go back to handing out the real address.
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