Email alias vs mailbox vs forwarding: what’s the difference?

A mailbox is a person: its own login, password and storage. An alias is another address that delivers into a mailbox you already have, so hello@ and billing@ need no extra login. Forwarding receives a message and sends a copy on to another address, often at another provider. Per-person pricing, which SuperMailOS uses, means you pay for mailboxes and never for aliases.

What is a mailbox?

One real inbox with its own address, login and storage: in practice, one person. It’s what every provider charges for, whether they call it a mailbox, a user or a seat. On SuperMailOS a mailbox costs $4 a month on Pro ($3 billed yearly).

What is an email alias?

An extra address with no login or storage of its own: mail sent to it lands in a mailbox. Aliases are how one person answers hello@, billing@ and press@ on several domains without several logins. On SuperMailOS an alias can live on any of your domains, and a reply goes out from the address the message came to.

What is a shared mailbox?

One mailbox several people work from, like support@. Everyone sees the same inbox, so a reply or a filed message is visible to the whole team. On SuperMailOS a shared mailbox counts as one mailbox, and giving teammates access to read, send or manage it costs nothing extra. On Microsoft 365, a shared mailbox needs no license up to 50 GB.

What is email forwarding, and when does it break?

Forwarding takes a message that has already arrived and re-sends a copy to another address. Two things go wrong with it. The forwarding server isn’t in the original sender’s SPF record, so SPF can fail at the next hop (DKIM usually survives if the message isn’t changed). And replying from the original address needs sending set up for it separately.

In SuperMailOS, forwarding is a filter rule: matching mail can be forwarded to up to five addresses. The copy is sent from your mailbox, with the original sender as Reply-To. It goes one hop only, never forwards mail that landed in spam, and passes through the same sending checks and DKIM signing as everything else you send.

What is a catch-all address, and does SuperMailOS have one?

A catch-all accepts mail for any address at a domain, including ones that were never set up, and drops it in one mailbox. It means a mistyped address still reaches you, but it also accepts every address a spammer guesses.

SuperMailOS doesn’t offer one. Mail to an address that isn’t a mailbox or an alias is rejected, so the sender gets a bounce instead of silence. Since aliases are free and unlimited, the alternative is to create one for each address you actually use.

How many aliases do providers include?

Which should you use?

• A person: a mailbox.
• A role address one person answers (hello@ on a side project): an alias into their mailbox.
• A role address a team answers (support@): a shared mailbox.
• A copy at another provider (an accountant’s inbox): a forwarding rule.
• Every address at a domain: on SuperMailOS, an alias for each one you use; there’s no catch-all.

Running several domains? Email hosting for multiple domains covers the setups and the DNS each domain needs.

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