Create and manage mailboxes

A mailbox is an address with its own storage, such as alex@example.com, that people sign in to with webmail or a mail app. Each Mail Hosting plan allows a number of mailboxes and a pool of storage they share. This page covers creating mailboxes and looking after them.

• A Mail Hosting service with a verified domain. See Add a domain to Mail Hosting.
• Room on the plan. The Mailboxes card shows how many the plan allows, such as 3 of 5 on this plan.

1. In the dashboard, go to Email, open the Mail Hosting service, then the Mailboxes tab.
2. Select Create mailbox….
3. In Name, enter the part before the @, such as alex. The hint under the field shows the full address.
4. In Domain, choose the domain. Only verified domains are listed.
5. Optionally, enter a Display name, such as Alex Morgan.
6. In Quota (GB), set the mailbox's storage. The field starts at an equal share of the plan's storage, and its hint shows the plan's total.
7. Under Password, choose Generate a strong password, or Set one now and enter it in New password (at least 12 characters).
8. Select Create mailbox.

A dialog shows the Address, the Password if we generated it, and the IMAP, SMTP and Webmail settings. Copy the password now: we show a generated password once and cannot show it again.

The mailbox appears in the list, with its Security, Quota, Password set and Enabled columns. To open it in webmail with its address filled in, open the menu at the end of its row and select Open webmail. To set up a mail app, see Connect a mail app to Mail Hosting.

1. On the Mailboxes tab, open the menu at the end of the mailbox's row.
2. Select Reset password….
3. Choose Generate a strong password, or Set one now and enter the new password.
4. Select Reset password.

The dialog that follows shows a generated password once. Resetting the password signs the mailbox out of webmail everywhere, and its app passwords keep working. Update the password in every mail app that uses it.

1. On the Mailboxes tab, open the menu at the end of the mailbox's row.
2. Select Change quota….
3. In Quota (GB), enter the new size. The hint shows the current quota and the plan's total.
4. Select Save quota.

The toast confirms the new quota. A quota is at least 100 MB, and all the mailboxes' quotas together cannot exceed the plan's storage. To give one mailbox more, shrink another first or move to a bigger plan.

On the Mailboxes tab, use the switch in the mailbox's Enabled column.

A mailbox you turn off cannot sign in, send or receive mail, and is signed out of webmail. Its stored mail stays, and turning it back on restores everything. A mailbox that is off still counts towards the plan.

1. On the Mailboxes tab, open the menu at the end of the mailbox's row.
2. Select Delete mailbox….
3. Type the mailbox's address to confirm, then select Delete mailbox.

The mailbox leaves the list, and its place and storage go back to the plan.

Create mailbox… is greyed out

The plan's mailboxes are all in use, or the service is not active. A full plan shows This plan allows 5 mailboxes. Delete one or change the plan to add another. Delete a mailbox, or move to a bigger plan.

Verify a domain first

The service has no verified domain yet, so the form has nothing to offer. Verify a domain first.

Use only letters, digits, dots, dashes, plus signs and underscores.

The name has another character, or starts or ends with a dot, dash, plus sign or underscore. Names are at most 64 characters and are stored in lower case.

That address already exists

The address is already a mailbox or an alias. Choose another name, or delete the alias first.

Not enough storage left on this plan for another mailbox of that size

The other mailboxes' quotas leave too little room. Enter a smaller Quota (GB), shrink another mailbox, or move to a bigger plan.

That would exceed the plan's total storage

The new quota does not fit beside the others. Shrink another mailbox first.

The domain is not registered in the mail engine yet; check the domain again in a minute

The domain was verified moments ago and its setup is not finished. Select Verify now on the domain's page, then try again.

The address shows a warning and the mailbox is off

We turn a mailbox off by ourselves when it suddenly sends far more than it usually does, which is what a stolen password looks like. The warning under the address says what we saw, and we email the account owner. Reset the password, then turn the mailbox back on. The warning stays under the address after that.

• Secure a mailbox
• Connect a mail app to Mail Hosting
• Move existing mail into a mailbox
• Forward addresses with aliases

Create a mailbox with a generated password:

curl -X POST https://api.coritan.com/api/v1/client/mail/4812/mailboxes \
  -H "Authorization: Bearer $CORITAN_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"domain_id": 311, "local_part": "alex", "display_name": "Alex Morgan", "quota_bytes": 5368709120}'

The body takes these fields:

domain_id

The domain, from GET /client/mail/{service_id}/domains. The API accepts a domain as soon as its ownership check has passed, before it is verified. See Move a domain that already receives mail.

local_part

The part before the @, 1–64 characters: letters, digits and . _ + -, starting and ending with a letter or digit.

password

Optional, 12–128 characters. Leave it out and we generate a 24-character password.

display_name

Optional, up to 255 characters.

quota_bytes

Optional, at least 104857600 (100 MB). Leave it out for an equal share of the plan's storage.

The answer is 201 with the mailbox. password holds the generated password, shown this once, or null when you set one:

{
  "id": 5120,
  "tenant_id": 902,
  "domain_id": 311,
  "kind": "mailbox",
  "address": "alex@example.com",
  "local_part": "alex",
  "display_name": "Alex Morgan",
  "quota_bytes": 5368709120,
  "targets": [],
  "status": "active",
  "password_set_at": "2026-09-16T10:52:03.418207+00:00",
  "created_at": "2026-09-16T10:52:03.418207+00:00",
  "totp_enabled": false,
  "app_passwords": 0,
  "frozen_reason": null,
  "user_id": null,
  "password": "q7!Rk2mV9x#Tz4pLw8=Hs3Nd"
}

The other operations:

A refused request answers 400 with one of the messages in Troubleshooting, or with This plan allows 5 mailboxes, Domain not found on this service or Prove you own example.com first: publish the ownership record shown under Domains, then check the domain. A value outside a field's range answers 422, an id that is not a mailbox on the service answers 404 Not found, and a failure on our side answers 502 with a message that starts Mail engine error:.

A relay has no mailboxes, but the same paths exist under /client/smtp-relay/{service_id}/mailboxes:

• GET answers {"items": []}, and POST answers 400 Mailboxes are only available on Mail Hosting services.
• .../{account_id}/password and .../{account_id}/enabled accept an SMTP credential's id and act on the credential. password is the only way to give a credential a password you choose; see Send over SMTP with credentials.
• Every other path under .../mailboxes/{account_id} answers 404 Not found.