> ## Documentation Index
> Fetch the complete documentation index at: https://hc.starbridge.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Allow Starbridge to connect Outlook inboxes

> Enable Authenticated SMTP on the mailboxes your team sends from, so they can connect Outlook to Starbridge Sequences.

<Note>
  Inbox connection is only used for sending Sequences directly from Starbridge. See [Connect your inbox](/sequences/connect-your-inbox) for the full workflow.
</Note>

<Tip>
  If a rep can't connect their Outlook inbox to Starbridge, this article is usually the fix.
</Tip>

If your team sends Sequences from Outlook, each mailbox needs **Authenticated SMTP** enabled in Microsoft 365. Starbridge connects with OAuth, but Exchange Online still refuses the send if this setting is off for the mailbox.

Microsoft recommends leaving Authenticated SMTP disabled and enabling it only for mailboxes that need it, so most mailboxes have it off by default. This is expected, not a sign anything is misconfigured.

<Warning>
  Unlike the Gmail equivalent, this is a **per-mailbox** setting, not a one-time tenant approval. Every rep who sends from Outlook needs it enabled on their own mailbox.
</Warning>

## Before you start

You need an account with administrator access to the Microsoft 365 admin center, or Exchange Online PowerShell access for the bulk approach. If you don't manage Microsoft 365 yourself, forward this page to whoever does.

You don't need to change Security Defaults. Starbridge doesn't use basic authentication.

## Enable Authenticated SMTP for a mailbox

<Steps>
  <Step title="Open the user in the admin center">
    Sign in to the [Microsoft 365 admin center](https://admin.microsoft.com) and go to **Users → Active users**. Select the user who needs to connect their inbox.
  </Step>

  <Step title="Open their email apps">
    In the flyout that appears, select **Mail**, then under **Email apps**, select **Manage email apps**.
  </Step>

  <Step title="Enable Authenticated SMTP and save">
    Check **Authenticated SMTP**, then select **Save changes**.

    Microsoft can take 30 to 40 minutes to reflect the change, so have the rep wait before trying to connect again.
  </Step>
</Steps>

## Enable it for several mailboxes at once

If you're onboarding a team, Exchange Online PowerShell is faster than clicking through each user:

<CodeGroup>
  ```powershell Enable for one mailbox theme={null}
  Set-CASMailbox -Identity <user> -SmtpClientAuthenticationDisabled $false
  ```
</CodeGroup>

Setting the value to `$false` enables Authenticated SMTP for that mailbox and overrides the organization-wide setting.

## Troubleshooting

<AccordionGroup>
  <Accordion title="The rep still can't connect after enabling it">
    Wait 30 to 40 minutes and try again. Microsoft can take that long to reflect the updated permissions, so an immediate retry often fails even though the setting is correct.

    If it still fails after that, Authenticated SMTP can be switched off at two levels, and the organization-wide setting can block a mailbox that looks correctly configured.

    Check the organization-wide setting in Exchange Online PowerShell:

    ```powershell theme={null}
    Get-TransportConfig | Format-List SmtpClientAuthenticationDisabled
    ```

    If this returns `True`, SMTP AUTH is disabled for the whole organization. Either enable it organization-wide, or confirm the per-mailbox override is set to `$false`, which takes precedence.

    You can also verify the mailbox itself:

    ```powershell theme={null}
    Get-CASMailbox -Identity <user> | Select SmtpClientAuthenticationDisabled
    ```

    A value of `True` means it's disabled for that mailbox. Blank means the mailbox follows the organization-wide setting.
  </Accordion>

  <Accordion title="The rep sees error 550 5.7.30">
    This means the connection attempted basic authentication, which Microsoft no longer supports for client submission. Starbridge uses OAuth, so if you see this, contact your GTME or [support@starbridge.ai](mailto:support@starbridge.ai).
  </Accordion>

  <Accordion title="Sending worked, then stopped">
    Tenant hardening often disables Authenticated SMTP across the organization or reverts per-mailbox exceptions. If sending stopped for everyone at once, check the organization-wide setting first.
  </Accordion>

  <Accordion title="Nothing here fixed it">
    Contact your GTME or [support@starbridge.ai](mailto:support@starbridge.ai).
  </Accordion>
</AccordionGroup>

## Where to go next

<Columns cols={2}>
  <Card title="Connect your inbox" icon="envelope" href="/sequences/connect-your-inbox">
    The full inbox connection workflow for Gmail and Outlook.
  </Card>

  <Card title="Allow Starbridge to connect Gmail inboxes" icon="google" href="/allow-stabridge-gmail-connections">
    The equivalent setup for Google Workspace.
  </Card>
</Columns>