Skip to main content
Inbox connection is only used for sending Sequences directly from Starbridge. See Connect your inbox for the full workflow.
If a rep can’t connect their Outlook inbox to Starbridge, this article is usually the fix.
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.
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.

​
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

1

Open the user in the admin center

Sign in to the Microsoft 365 admin center and go to Users → Active users. Select the user who needs to connect their inbox.
2

Open their email apps

In the flyout that appears, select Mail, then under Email apps, select Manage email apps.
3

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.

​
Enable it for several mailboxes at once

If you’re onboarding a team, Exchange Online PowerShell is faster than clicking through each user:
Setting the value to $false enables Authenticated SMTP for that mailbox and overrides the organization-wide setting.

​
Troubleshooting

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:
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:
A value of True means it’s disabled for that mailbox. Blank means the mailbox follows the organization-wide setting.
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.
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.
Contact your GTME or support@starbridge.ai.

​
Where to go next

Connect your inbox

The full inbox connection workflow for Gmail and Outlook.

Allow Starbridge to connect Gmail inboxes

The equivalent setup for Google Workspace.