How to Enable SMTP Authentication for Office 365 to Send Emails via SMTP

If you need to send emails using Office 365 SMTP credentials (e.g., from a website, app, or third-party email client), you must ensure certain settings are correctly configured both in Microsoft 365 and Azure. This guide walks you through the complete set

If you're integrating Microsoft 365 SMTP with custom applications, websites, or legacy systems, you may need to enable SMTP AUTH for specific mailboxes. Microsoft has updated several authentication and security configurations, so older setup methods may no longer work.

Follow the updated steps below to properly enable SMTP AUTH using PowerShell.

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🧰 Prerequisites

Before starting, ensure you have:

• Administrator access to Microsoft 365

• Windows PowerShell installed

• Internet connectivity to connect with Exchange Online

Please make sure to open PowerShell as Administrator before running the commands.

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🔧 Step 1: Install Exchange Online Management Module

Run the following command:

Install-Module -Name ExchangeOnlineManagement

If prompted to install from an untrusted repository, type:

Y

and press Enter.

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🔧 Step 2: Import the Module

Import-Module ExchangeOnlineManagement

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🔧 Step 3: Set Execution Policy

If script execution is restricted, run:

Set-ExecutionPolicy Unrestricted

Confirm by typing:

Y

when prompted.

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🔐 Step 4: Connect to Exchange Online

Connect-ExchangeOnline

This command will prompt you to log in using your Microsoft 365 administrator credentials.

You can also connect directly using:

Connect-ExchangeOnline -UserPrincipalName admin@yourdomain.com

Replace admin@yourdomain.com with your Microsoft 365 admin email address.

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📧 Step 5: Check Global SMTP AUTH Status

Run the following command:

Get-TransportConfig | Select SmtpClientAuthenticationDisabled

Understanding the Result

• True → SMTP AUTH is disabled globally.

• False → SMTP AUTH is enabled globally.

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✅ Step 6: Enable SMTP AUTH for a Specific Mailbox

To enable SMTP AUTH for a specific user mailbox:

Set-CASMailbox -Identity user@yourdomain.com -SmtpClientAuthenticationDisabled $false

Replace user@yourdomain.com with the actual mailbox email address.

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🔍 Step 7: Verify SMTP AUTH Status

Run the following command to confirm the configuration:

Get-CASMailbox -Identity user@yourdomain.com | Select SmtpClientAuthenticationDisabled

Expected Result

False

This means SMTP AUTH is successfully enabled for that mailbox.

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✅ Configuration Complete

SMTP AUTH is now enabled for the selected mailbox, and you can use Microsoft 365 SMTP settings within your applications, contact forms, ERP systems, or legacy integrations.

This updated method aligns with Microsoft’s latest Exchange Online security and authentication policies.