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Sending from your aliases and +tag addresses

You can send from any address that is yours:

• your own address;
• any of your aliases;
• any of those with a +tag, such as amy+shop@example.com.

Nobody can send from someone else's address, alias or +tag address, in webmail, from a mail app (SMTP), or through JMAP. The server refuses it and says why. See What stops anyone sending as you.

In webmail

Pick the address under From. To use a +tag, type it in the +tag box next to it (letters, digits, ., _ and -, starting and ending with a letter or digit). When you reply to mail that was sent to one of your +tag addresses, the reply goes out from that same address.

A default From

To have new messages start from an alias or a +tag address, open Settings → Default From, pick the address, type a +tag if you want one (such as shop for you+shop@example.com) and Save. You can still pick another address under From on any message, and replies keep answering from the address the mail was sent to. Clear the +tag and pick your own address to go back.

Only your own addresses and aliases can be chosen; if an alias you chose is removed later, new messages start from your own address again. Your administrator can see or set it too (corpsuite mailbox default-from), but only to one of your own addresses.

What stops anyone sending as you

Every message sent from here, whichever way it is sent, is checked before it leaves:

• The envelope sender, every From address, and any Sender, Resent-From or Resent-Sender must be the sender's own address or alias (with or without a +tag). A +tag on someone else's address, such as bob+amy@, is someone else's.
• A sender name that shows an address, such as "boss@example.com" <amy@example.com>, must show one of the sender's own; many mail apps show the name in place of the address.
• Sender names saved in Settings → Names and signatures follow the same rule.

Mail from other servers that claims to be from one of your organization's proved domains is refused unless it is authenticated as that domain (SPF or DKIM), even if the domain's DMARC policy is only none: everyone on it sends through this server. See SPF, DKIM and DMARC.

In a mail app

Set the app's "From" or "identity" to the alias or +tag address, and keep signing in with your own address (or an app password). The address in the message's From and the one the app gives the server must both be yours.

Aliases or another mailbox?

• An alias is another address for a mailbox you have: mail to it lands in that mailbox's inbox, and you can send from it. It takes no seat.
• An extra mailbox is a separate inbox with its own folders and settings, which you switch to from the picker at the top. It takes a seat. See Several mailboxes for one person.

If you have several mailboxes, each alias says which one it delivers to: choose it when you add the alias, and change it later from the list next to the alias.

Adding your own aliases

If your plan includes Own aliases, open Settings → Aliases in webmail to add or remove aliases. They can be on your organization's domains or, for free accounts, on the shared domains offered here; reserved names (such as postmaster or noreply) are not available. Each user may have a set number of aliases, and the organization a total:

• Aliases per user and aliases for the whole tenant are set on the plan by the platform administrator.
• An administrator can give one user a different number under Limits next to the user (maxAliases).

Aliases an administrator adds count toward the same limits.