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Create Mailboxes

TenantCore can create sending mailboxes under domains already registered to a connected tenant. Each domain supports up to 3 mailboxes.

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Before you begin

You need:
  • a connected Microsoft 365 tenant
  • a domain already added to that tenant
  • available mailbox capacity
  • a domain sufficiently prepared for the workflow you intend to use

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Create a mailbox

  1. Open Mailboxes or the mailbox view for the domain.
  2. Choose Create mailbox.
  3. Enter the mailbox details requested by TenantCore.
  4. Submit the request.
TenantCore creates the mailbox in Microsoft 365 and creates the corresponding TenantCore mailbox resource.

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After creation

The mailbox can then be used for:
  • password access/reset
  • optional MFA setup
  • send-limit configuration
  • Outlook delegation
  • sending-platform connection
  • monitoring and Reports

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Credential handling

TenantCore protects mailbox credentials through its secure credential-vault workflow. Do not build an external spreadsheet-based password process around mailbox creation. Use TenantCore’s credential controls when you need the password.

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Mailbox ownership

Every mailbox is attached to:
This relationship is also enforced by the Complete API. An arbitrary external mailbox cannot be submitted to TenantCore and managed as though it belonged to the account.

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If creation fails

Check:
  • the domain still belongs to the connected tenant
  • mailbox capacity has not been reached
  • Microsoft/Exchange access is healthy
  • the address is not already in use
  • TenantCore has the required application permissions
Correct the underlying condition and retry the supported TenantCore workflow.