An email alias is an address that forwards to an inbox you already read. Mail sent to it arrives where your mail normally arrives. There is no second inbox to check, no app to install, and nothing to migrate. The alias is a front door; your real address stays the building.
That is the whole idea, and everything else here is a consequence of it. Hand a different address to every service you sign up to, and each one holds a different piece of paper with a different name on it. When one leaks, you know which, and you can close that door without moving house.
How forwarding actually works
A sender types your alias and their mail server looks up where to deliver it. The answer is the alias service, which accepts the message, looks up which real inbox that alias belongs to, and passes it on. Your provider receives it like any other mail.
- You create shop.k4x2@example.com and point it at the inbox you already use.
- A retailer sends a receipt to that address.
- Their server delivers it to the alias service, which is that address’s mail host.
- The service looks up the destination and forwards the message on.
- It lands in your normal inbox, in your normal mail app, on your normal phone.
Two details decide how much a service is really doing for you. The first is what happens to the message itself: some services store forwarded mail, others pass it through and keep only a delivery record. The second is what happens when you reply, which is the part most people discover late.
Aliases and replies: the part people get wrong
Forwarding one way is easy. The hard direction is answering. Hit Reply on a forwarded message and your mail app sends from your real address, so the person you were hiding it from now has it. That single reply undoes every alias you ever made for that contact.
Good alias services solve this by giving each conversation a reply address of its own. Your reply goes back through the service, which sends it onward as the alias. Done properly this needs no configuration: you press Reply in Gmail or Apple Mail exactly as you always do, and the recipient sees the alias.
There is one honest exception across the whole category. Reply All includes the other people on the thread, and those are ordinary addresses in your mail app, so replies to them go direct. If a thread has several recipients and you need to stay masked, reply to the sender only.
Starting a brand new email as your alias is a different job from replying, and it does usually need setup, which in Gmail looks like this: you add the alias to your mail app as a sending identity using SMTP details the service gives you. Worth knowing before you assume a service cannot do it, and worth knowing you do not need it merely to answer.
Alias versus a second email account
The instinct to open a throwaway Gmail for signups is a good one, and it fails for a boring reason: it is a second inbox. You have to remember to check it, and within a month it is either ignored or it has become a real inbox with real mail you cannot abandon.
It also fails at the thing you wanted. A junk account is still one address given to hundreds of services, so when it leaks you learn nothing about who leaked it, and you cannot switch it off without losing everything attached to it. You have moved the problem and bought a second inbox to check.
A second account is genuinely useful for separating a role rather than a risk: one for work, one for a side project, one for a club. That is a filing decision. Aliases are for the other problem, where you want many addresses and exactly one inbox.
Alias versus temporary or disposable mail
Temp-mail sites give you an address that works for ten minutes and then stops existing. For reading one confirmation code and never returning, they are the right tool and nothing here argues otherwise.
They fail the moment the account matters. The address expires, so a password-reset link six months later has nowhere to go, and the account goes with it. Many sites also block the well-known disposable domains outright, so the signup fails before it starts.
An alias is the opposite trade, and it is the structural answer to spam that filters never quite stop: a permanent address on an ordinary domain, kept for as long as you want it, with an off switch instead of an expiry date. You decide when it dies, rather than a timer.
Alias versus Gmail plus-addressing
If your address is you@gmail.com then you+shop@gmail.com already reaches you. It is a convention rather than a standard, supported by Gmail, Outlook and Fastmail among others, and it is free and instant. For sorting your own mail into folders it is excellent.
As a privacy measure it has two flaws, and they are structural rather than fixable. Deleting everything after the plus sign is one line of code, so any list broker who wants your base address has it. And the base address is visible in the alias itself: you+shop@gmail.com announces that you@gmail.com exists.
It also cannot be switched off. There is no way to stop you+shop@gmail.com working except to filter it after delivery, so the mail still arrives and you are back to sorting. Use plus-addressing to organise; use aliases when the address itself needs to be separable from you.
Shared domain or your own domain
Alias services offer addresses on a domain they own, shared with all their customers, and most also let you bring a domain you own. The choice matters more than it first appears.
A shared domain needs no setup and works in about a minute. The trade-offs: the good names are contested, providers cap how many you can take, and some websites refuse the well-known alias domains for the same reason they refuse temp mail. You are also tied to that provider, because leaving takes the addresses with it.
Your own domain removes all four problems. Addresses look like ordinary mailboxes because they are on an ordinary domain, so nothing rejects them; the namespace is yours, which is why services can offer genuinely unlimited aliases there; and if you change provider you repoint DNS and keep every address. The cost is a domain registration and ten minutes with your DNS records.
If you already own a domain, use it. If you do not, a shared domain is a perfectly good place to start, and the addresses you make there are not wasted work.
What to look for in a service
The category looks uniform from the pricing page and is not. Six questions separate them, and they are worth asking before you hand over the address you use for your bank.
- Does replying work without setup, and what does the recipient see when you do?
- Is message content stored, or only a delivery record? Ask how long each is kept.
- Can you bring your own domain, and on which plan?
- What happens to your aliases if you stop paying: do they keep forwarding, or stop?
- Can you turn a single alias off, and is mail then refused or silently binned?
- When "unlimited" appears, unlimited where? On your own domain, on theirs, or both?
The fourth is the one people skip and regret. Aliases become the address of record for dozens of accounts, so a service that stops forwarding the day you cancel is holding those accounts hostage. Ask before you depend on it, not after.
When an alias is the wrong tool
Two cases deserve care. The first is any account where losing access would be serious and recovery runs through email: banks, government portals, your domain registrar. An alias works there and gives you a useful phishing signal, because mail from your bank arriving on the wrong alias is definitionally fake. But disable that alias later and forget, and you have locked yourself out of a live account. Use your own domain for those, and never point them at an address you might switch off.
The second is anywhere a human reads the address back to you. Support calls and delivery drivers cope badly with shop.k4x2@example.com. Keep a readable alias for those.